Merge pull request #299 from hecht-a/theme_switcher

feat: theme switcher

docs/configuration.md

@@ -325,6 +325,19 @@ theme:
   background-color: 100 20 10
   primary-color: 40 90 40
   contrast-multiplier: 1.1
+
+  presets:
+    gruvbox-dark:
+      background-color: 0 0 16
+      primary-color: 43 59 81
+      positive-color: 61 66 44
+      negative-color: 6 96 59
+
+    zebra:
+      light: true
+      background-color: 0 0 95
+      primary-color: 0 0 10
+      negative-color: 0 90 50
 ```
 
 ### Available themes
@@ -341,6 +354,7 @@ If you don't want to spend time configuring your own theme, there are [several a
 | contrast-multiplier | number | no | 1 |
 | text-saturation-multiplier | number | no | 1 |
 | custom-css-file | string | no | |
+| presets | object | no | |
 
 #### `light`
 Whether the scheme is light or dark. This does not change the background color, it inverts the text colors so that they look appropriately on a light background.
@@ -385,6 +399,30 @@ theme:
 >
 > In addition, you can also use the `css-class` property which is available on every widget to set custom class names for individual widgets.
 
+#### `presets`
+Define additional theme presets that can be selected from the theme switcher on the page. For each preset, you can specify the same properties as for the default theme, such as `background-color`, `primary-color`, `positive-color`, `negative-color`, `contrast-multiplier`, etc., except for the `custom-css-file` property.
+
+Example:
+
+```yaml
+theme:
+  presets:
+    my-custom-dark-theme:
+      background-color: 229 19 23
+      contrast-multiplier: 1.2
+      primary-color: 222 74 74
+      positive-color: 96 44 68
+      negative-color: 359 68 71
+    my-custom-light-theme:
+      light: true
+      background-color: 220 23 95
+      contrast-multiplier: 1.1
+      primary-color: 220 91 54
+      positive-color: 109 58 40
+      negative-color: 347 87 44
+```
+
+To override the default dark and light themes, use the key names `default-dark` and `default-light`.
 
 ## Pages & Columns
 ![illustration of pages and columns](images/pages-and-columns-illustration.png)
@@ -415,7 +453,6 @@ pages:
 | desktop-navigation-width | string | no | |
 | center-vertically | boolean | no | false |
 | hide-desktop-navigation | boolean | no | false |
-| expand-mobile-page-navigation | boolean | no | false |
 | show-mobile-header | boolean | no | false |
 | columns | array | yes | |
 
@@ -447,9 +484,6 @@ When set to `true`, vertically centers the content on the page. Has no effect if
 #### `hide-desktop-navigation`
 Whether to show the navigation links at the top of the page on desktop.
 
-#### `expand-mobile-page-navigation`
-Whether the mobile page navigation should be expanded by default.
-
 #### `show-mobile-header`
 Whether to show a header displaying the name of the page on mobile. The header purposefully has a lot of vertical whitespace in order to push the content down and make it easier to reach on tall devices.
 

internal/glance/config-fields.go

@@ -23,17 +23,27 @@ const (
 )
 
 type hslColorField struct {
-	Hue        float64
+	H float64
-	Saturation float64
+	S float64
-	Lightness  float64
+	L float64
 }
 
 func (c *hslColorField) String() string {
-	return fmt.Sprintf("hsl(%.1f, %.1f%%, %.1f%%)", c.Hue, c.Saturation, c.Lightness)
+	return fmt.Sprintf("hsl(%.1f, %.1f%%, %.1f%%)", c.H, c.S, c.L)
 }
 
 func (c *hslColorField) ToHex() string {
-	return hslToHex(c.Hue, c.Saturation, c.Lightness)
+	return hslToHex(c.H, c.S, c.L)
+}
+
+func (c1 *hslColorField) SameAs(c2 *hslColorField) bool {
+	if c1 == nil && c2 == nil {
+		return true
+	}
+	if c1 == nil || c2 == nil {
+		return false
+	}
+	return c1.H == c2.H && c1.S == c2.S && c1.L == c2.L
 }
 
 func (c *hslColorField) UnmarshalYAML(node *yaml.Node) error {
@@ -76,9 +86,9 @@ func (c *hslColorField) UnmarshalYAML(node *yaml.Node) error {
 		return fmt.Errorf("HSL lightness must be between 0 and %d", hslLightnessMax)
 	}
 
-	c.Hue = hue
+	c.H = hue
-	c.Saturation = saturation
+	c.S = saturation
-	c.Lightness = lightness
+	c.L = lightness
 
 	return nil
 }

internal/glance/config.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"fmt"
 	"html/template"
+	"iter"
 	"log"
 	"maps"
 	"os"
@@ -38,15 +39,9 @@ type config struct {
 	} `yaml:"document"`
 
 	Theme struct {
-		BackgroundColor          *hslColorField `yaml:"background-color"`
+		themeProperties `yaml:",inline"`
-		BackgroundColorAsHex     string         `yaml:"-"`
+		CustomCSSFile   string                                   `yaml:"custom-css-file"`
-		PrimaryColor             *hslColorField `yaml:"primary-color"`
+		Presets         orderedYAMLMap[string, *themeProperties] `yaml:"presets"`
-		PositiveColor            *hslColorField `yaml:"positive-color"`
-		NegativeColor            *hslColorField `yaml:"negative-color"`
-		Light                    bool           `yaml:"light"`
-		ContrastMultiplier       float32        `yaml:"contrast-multiplier"`
-		TextSaturationMultiplier float32        `yaml:"text-saturation-multiplier"`
-		CustomCSSFile            string         `yaml:"custom-css-file"`
 	} `yaml:"theme"`
 
 	Branding struct {
@@ -64,15 +59,14 @@ type config struct {
 }
 
 type page struct {
-	Title                      string `yaml:"name"`
+	Title                  string `yaml:"name"`
-	Slug                       string `yaml:"slug"`
+	Slug                   string `yaml:"slug"`
-	Width                      string `yaml:"width"`
+	Width                  string `yaml:"width"`
-	DesktopNavigationWidth     string `yaml:"desktop-navigation-width"`
+	DesktopNavigationWidth string `yaml:"desktop-navigation-width"`
-	ShowMobileHeader           bool   `yaml:"show-mobile-header"`
+	ShowMobileHeader       bool   `yaml:"show-mobile-header"`
-	ExpandMobilePageNavigation bool   `yaml:"expand-mobile-page-navigation"`
+	HideDesktopNavigation  bool   `yaml:"hide-desktop-navigation"`
-	HideDesktopNavigation      bool   `yaml:"hide-desktop-navigation"`
+	CenterVertically       bool   `yaml:"center-vertically"`
-	CenterVertically           bool   `yaml:"center-vertically"`
+	Columns                []struct {
-	Columns                    []struct {
 		Size    string  `yaml:"size"`
 		Widgets widgets `yaml:"widgets"`
 	} `yaml:"columns"`
@@ -490,3 +484,103 @@ func isConfigStateValid(config *config) error {
 
 	return nil
 }
+
+// Read-only way to store ordered maps from a YAML structure
+type orderedYAMLMap[K comparable, V any] struct {
+	keys []K
+	data map[K]V
+}
+
+func newOrderedYAMLMap[K comparable, V any](keys []K, values []V) (*orderedYAMLMap[K, V], error) {
+	if len(keys) != len(values) {
+		return nil, fmt.Errorf("keys and values must have the same length")
+	}
+
+	om := &orderedYAMLMap[K, V]{
+		keys: make([]K, len(keys)),
+		data: make(map[K]V, len(keys)),
+	}
+
+	copy(om.keys, keys)
+
+	for i := range keys {
+		om.data[keys[i]] = values[i]
+	}
+
+	return om, nil
+}
+
+func (om *orderedYAMLMap[K, V]) Items() iter.Seq2[K, V] {
+	return func(yield func(K, V) bool) {
+		for _, key := range om.keys {
+			value, ok := om.data[key]
+			if !ok {
+				continue
+			}
+			if !yield(key, value) {
+				return
+			}
+		}
+	}
+}
+
+func (om *orderedYAMLMap[K, V]) Get(key K) (V, bool) {
+	value, ok := om.data[key]
+	return value, ok
+}
+
+func (self *orderedYAMLMap[K, V]) Merge(other *orderedYAMLMap[K, V]) *orderedYAMLMap[K, V] {
+	merged := &orderedYAMLMap[K, V]{
+		keys: make([]K, 0, len(self.keys)+len(other.keys)),
+		data: make(map[K]V, len(self.data)+len(other.data)),
+	}
+
+	merged.keys = append(merged.keys, self.keys...)
+	maps.Copy(merged.data, self.data)
+
+	for _, key := range other.keys {
+		if _, exists := self.data[key]; !exists {
+			merged.keys = append(merged.keys, key)
+		}
+	}
+	maps.Copy(merged.data, other.data)
+
+	return merged
+}
+
+func (om *orderedYAMLMap[K, V]) UnmarshalYAML(node *yaml.Node) error {
+	if node.Kind != yaml.MappingNode {
+		return fmt.Errorf("orderedMap: expected mapping node, got %d", node.Kind)
+	}
+
+	if len(node.Content)%2 != 0 {
+		return fmt.Errorf("orderedMap: expected even number of content items, got %d", len(node.Content))
+	}
+
+	om.keys = make([]K, len(node.Content)/2)
+	om.data = make(map[K]V, len(node.Content)/2)
+
+	for i := 0; i < len(node.Content); i += 2 {
+		keyNode := node.Content[i]
+		valueNode := node.Content[i+1]
+
+		var key K
+		if err := keyNode.Decode(&key); err != nil {
+			return fmt.Errorf("orderedMap: decoding key: %v", err)
+		}
+
+		if _, ok := om.data[key]; ok {
+			return fmt.Errorf("orderedMap: duplicate key %v", key)
+		}
+
+		var value V
+		if err := valueNode.Decode(&value); err != nil {
+			return fmt.Errorf("orderedMap: decoding value: %v", err)
+		}
+
+		(*om).keys[i/2] = key
+		(*om).data[key] = value
+	}
+
+	return nil
+}

internal/glance/embed.go

@@ -82,7 +82,6 @@ func computeFSHash(files fs.FS) (string, error) {
 
 var cssImportPattern = regexp.MustCompile(`(?m)^@import "(.*?)";$`)
 var cssSingleLineCommentPattern = regexp.MustCompile(`(?m)^\s*\/\*.*?\*\/$`)
-var whitespaceAtBeginningOfLinePattern = regexp.MustCompile(`(?m)^\s+`)
 
 // Yes, we bundle at runtime, give comptime pls
 var bundledCSSContents = func() []byte {

internal/glance/glance.go

@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"context"
 	"fmt"
-	"html/template"
 	"log"
 	"net/http"
 	"path/filepath"
@@ -15,19 +14,17 @@ import (
 )
 
 var (
-	pageTemplate           = mustParseTemplate("page.html", "document.html")
+	pageTemplate        = mustParseTemplate("page.html", "document.html")
-	pageContentTemplate    = mustParseTemplate("page-content.html")
+	pageContentTemplate = mustParseTemplate("page-content.html")
-	pageThemeStyleTemplate = mustParseTemplate("theme-style.gotmpl")
+	manifestTemplate    = mustParseTemplate("manifest.json")
-	manifestTemplate       = mustParseTemplate("manifest.json")
 )
 
 const STATIC_ASSETS_CACHE_DURATION = 24 * time.Hour
 
 type application struct {
-	Version          string
+	Version   string
-	CreatedAt        time.Time
+	CreatedAt time.Time
-	Config           config
+	Config    config
-	ParsedThemeStyle template.HTML
 
 	parsedManifest []byte
 
@@ -35,14 +32,15 @@ type application struct {
 	widgetByID map[uint64]widget
 }
 
-func newApplication(config *config) (*application, error) {
+func newApplication(c *config) (*application, error) {
 	app := &application{
 		Version:    buildVersion,
 		CreatedAt:  time.Now(),
-		Config:     *config,
+		Config:     *c,
 		slugToPage: make(map[string]*page),
 		widgetByID: make(map[uint64]widget),
 	}
+	config := &app.Config
 
 	app.slugToPage[""] = &config.Pages[0]
 
@@ -50,10 +48,43 @@ func newApplication(config *config) (*application, error) {
 		assetResolver: app.StaticAssetPath,
 	}
 
-	var err error
+	//
-	app.ParsedThemeStyle, err = executeTemplateToHTML(pageThemeStyleTemplate, &app.Config.Theme)
+	// Init themes
+	//
+
+	themeKeys := make([]string, 0, 2)
+	themeProps := make([]*themeProperties, 0, 2)
+
+	defaultDarkTheme, ok := config.Theme.Presets.Get("default-dark")
+	if ok && !config.Theme.SameAs(defaultDarkTheme) || !config.Theme.SameAs(&themeProperties{}) {
+		themeKeys = append(themeKeys, "default-dark")
+		themeProps = append(themeProps, &themeProperties{})
+	}
+
+	themeKeys = append(themeKeys, "default-light")
+	themeProps = append(themeProps, &themeProperties{
+		Light:           true,
+		BackgroundColor: &hslColorField{240, 13, 86},
+		PrimaryColor:    &hslColorField{45, 100, 26},
+		NegativeColor:   &hslColorField{0, 50, 50},
+	})
+
+	themePresets, err := newOrderedYAMLMap(themeKeys, themeProps)
 	if err != nil {
-		return nil, fmt.Errorf("parsing theme style: %v", err)
+		return nil, fmt.Errorf("creating theme presets: %v", err)
+	}
+	config.Theme.Presets = *themePresets.Merge(&config.Theme.Presets)
+
+	for key, properties := range config.Theme.Presets.Items() {
+		properties.Key = key
+		if err := properties.init(); err != nil {
+			return nil, fmt.Errorf("initializing preset theme %s: %v", key, err)
+		}
+	}
+
+	config.Theme.Key = "default"
+	if err := config.Theme.init(); err != nil {
+		return nil, fmt.Errorf("initializing default theme: %v", err)
 	}
 
 	for p := range config.Pages {
@@ -90,18 +121,10 @@ func newApplication(config *config) (*application, error) {
 		}
 	}
 
-	config = &app.Config
-
 	config.Server.BaseURL = strings.TrimRight(config.Server.BaseURL, "/")
 	config.Theme.CustomCSSFile = app.resolveUserDefinedAssetPath(config.Theme.CustomCSSFile)
 	config.Branding.LogoURL = app.resolveUserDefinedAssetPath(config.Branding.LogoURL)
 
-	if config.Theme.BackgroundColor != nil {
-		config.Theme.BackgroundColorAsHex = config.Theme.BackgroundColor.ToHex()
-	} else {
-		config.Theme.BackgroundColorAsHex = "#151519"
-	}
-
 	if config.Branding.FaviconURL == "" {
 		config.Branding.FaviconURL = app.StaticAssetPath("favicon.png")
 	} else {
@@ -120,11 +143,11 @@ func newApplication(config *config) (*application, error) {
 		config.Branding.AppBackgroundColor = config.Theme.BackgroundColorAsHex
 	}
 
-	var manifestWriter bytes.Buffer
+	manifest, err := executeTemplateToString(manifestTemplate, pageTemplateData{App: app})
-	if err := manifestTemplate.Execute(&manifestWriter, pageTemplateData{App: app}); err != nil {
+	if err != nil {
 		return nil, fmt.Errorf("parsing manifest.json: %v", err)
 	}
-	app.parsedManifest = manifestWriter.Bytes()
+	app.parsedManifest = []byte(manifest)
 
 	return app, nil
 }
@@ -162,9 +185,28 @@ func (a *application) resolveUserDefinedAssetPath(path string) string {
 	return path
 }
 
+type pageTemplateRequestData struct {
+	Theme *themeProperties
+}
+
 type pageTemplateData struct {
-	App  *application
+	App     *application
-	Page *page
+	Page    *page
+	Request pageTemplateRequestData
+}
+
+func (a *application) populateTemplateRequestData(data *pageTemplateRequestData, r *http.Request) {
+	theme := &a.Config.Theme.themeProperties
+
+	selectedTheme, err := r.Cookie("theme")
+	if err == nil {
+		preset, exists := a.Config.Theme.Presets.Get(selectedTheme.Value)
+		if exists {
+			theme = preset
+		}
+	}
+
+	data.Theme = theme
 }
 
 func (a *application) handlePageRequest(w http.ResponseWriter, r *http.Request) {
@@ -175,13 +217,14 @@ func (a *application) handlePageRequest(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
-	pageData := pageTemplateData{
+	data := pageTemplateData{
 		Page: page,
 		App:  a,
 	}
+	a.populateTemplateRequestData(&data.Request, r)
 
 	var responseBytes bytes.Buffer
-	err := pageTemplate.Execute(&responseBytes, pageData)
+	err := pageTemplate.Execute(&responseBytes, data)
 	if err != nil {
 		w.WriteHeader(http.StatusInternalServerError)
 		w.Write([]byte(err.Error()))
@@ -266,6 +309,7 @@ func (a *application) server() (func() error, func() error) {
 	mux.HandleFunc("GET /{page}", a.handlePageRequest)
 
 	mux.HandleFunc("GET /api/pages/{page}/content/{$}", a.handlePageContentRequest)
+	mux.HandleFunc("POST /api/set-theme/{key}", a.handleThemeChangeRequest)
 	mux.HandleFunc("/api/widgets/{widget}/{path...}", a.handleWidgetRequest)
 	mux.HandleFunc("GET /api/healthz", func(w http.ResponseWriter, _ *http.Request) {
 		w.WriteHeader(http.StatusOK)

internal/glance/static/css/mobile.css

@@ -48,6 +48,17 @@
         transition: transform .3s;
     }
 
+    .mobile-navigation-actions > * {
+        padding-block: .9rem;
+        padding-inline: var(--content-bounds-padding);
+        cursor: pointer;
+        transition: background-color .3s;
+    }
+
+    .mobile-navigation-actions > *:hover, .mobile-navigation-actions > *:active {
+        background-color: var(--color-widget-background-highlight);
+    }
+
     .mobile-navigation:has(.mobile-navigation-page-links-input:checked) .hamburger-icon {
         --spacing: 7px;
         color: var(--color-primary);
@@ -60,6 +71,7 @@
 
     .mobile-navigation-page-links {
         border-top: 1px solid var(--color-widget-content-border);
+        border-bottom: 1px solid var(--color-widget-content-border);
         padding: 20px var(--content-bounds-padding);
         display: flex;
         align-items: center;

internal/glance/static/css/site.css

@@ -1,4 +1,4 @@
-.light-scheme {
+:root[data-scheme=light] {
     --scheme: 100% -;
 }
 
@@ -219,7 +219,7 @@ kbd:active {
     max-width: 1100px;
 }
 
-.page-center-vertically .page {
+.page.center-vertically {
     display: flex;
     justify-content: center;
     flex-direction: column;
@@ -256,6 +256,8 @@ kbd:active {
 }
 
 .nav {
+    overflow-x: auto;
+    min-width: 0;
     height: 100%;
     gap: var(--header-items-gap);
 }
@@ -293,3 +295,73 @@ kbd:active {
     border-bottom-color: var(--color-primary);
     color: var(--color-text-highlight);
 }
+
+.theme-choices {
+    --presets-per-row: 2;
+    display: grid;
+    grid-template-columns: repeat(var(--presets-per-row), 1fr);
+    align-items: center;
+    gap: 1.35rem;
+}
+
+.theme-choices:has(> :nth-child(3)) {
+    --presets-per-row: 3;
+}
+
+.theme-preset {
+    background-color: var(--color);
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    gap: 0.5rem;
+    height: 2rem;
+    padding-inline: 0.5rem;
+    border-radius: 0.3rem;
+    border: none;
+    cursor: pointer;
+    position: relative;
+}
+
+.theme-choices .theme-preset::before {
+    content: '';
+    position: absolute;
+    inset: -.4rem;
+    border-radius: .7rem;
+    border: 2px solid transparent;
+    transition: border-color .3s;
+}
+
+.theme-choices .theme-preset:hover::before {
+    border-color: var(--color-text-subdue);
+}
+
+.theme-choices .theme-preset.current::before {
+    border-color: var(--color-text-base);
+}
+
+.theme-preset-light {
+    gap: 0.3rem;
+    height: 1.8rem;
+}
+
+.theme-color {
+    background-color: var(--color);
+    width: 0.9rem;
+    height: 0.9rem;
+    border-radius: 0.2rem;
+}
+
+.theme-preset-light .theme-color {
+    width: 1rem;
+    height: 1rem;
+    border-radius: 0.3rem;
+}
+
+.current-theme-preview {
+    opacity: 0.4;
+    transition: opacity .3s;
+}
+
+.theme-picker.popover-active .current-theme-preview, .theme-picker:hover {
+    opacity: 1;
+}

internal/glance/static/css/utils.css

@@ -376,7 +376,7 @@ details[open] .summary::after {
     gap: 0.5rem;
 }
 
-:root:not(.light-scheme) .flat-icon {
+:root:not([data-scheme=light]) .flat-icon {
     filter: invert(1);
 }
 
@@ -459,6 +459,23 @@ details[open] .summary::after {
     filter: none;
 }
 
+
+.hide-scrollbars {
+    scrollbar-width: none;
+}
+
+/* Hide on Safari and Chrome */
+.hide-scrollbars::-webkit-scrollbar {
+    display: none;
+}
+
+.ui-icon {
+    width: 2.3rem;
+    height: 2.3rem;
+    display: block;
+    flex-shrink: 0;
+}
+
 .size-h1 { font-size: var(--font-size-h1); }
 .size-h2 { font-size: var(--font-size-h2); }
 .size-h3 { font-size: var(--font-size-h3); }
@@ -510,6 +527,7 @@ details[open] .summary::after {
 .grow { flex-grow: 1; }
 .flex-column { flex-direction: column; }
 .items-center { align-items: center; }
+.self-center { align-self: center; }
 .items-start { align-items: start; }
 .items-end { align-items: end; }
 .gap-5 { gap: 0.5rem; }
@@ -549,6 +567,7 @@ details[open] .summary::after {
 .padding-widget { padding: var(--widget-content-padding); }
 .padding-block-widget { padding-block: var(--widget-content-vertical-padding); }
 .padding-inline-widget { padding-inline: var(--widget-content-horizontal-padding); }
+.pointer-events-none { pointer-events: none; }
 .padding-block-5 { padding-block: 0.5rem; }
 .scale-half { transform: scale(0.5); }
 .list { --list-half-gap: 0rem; }

internal/glance/static/js/main.js

@@ -1,6 +1,7 @@
 import { setupPopovers } from './popover.js';
 import { setupMasonries } from './masonry.js';
 import { throttledDebounce, isElementVisible, openURLInNewTab } from './utils.js';
+import { elem, find, findAll } from './templating.js';
 
 async function fetchPageContent(pageData) {
     // TODO: handle non 200 status codes/time outs
@@ -654,7 +655,77 @@ function setupTruncatedElementTitles() {
     }
 }
 
+async function changeTheme(key, onChanged) {
+    const themeStyleElem = find("#theme-style");
+
+    const response = await fetch(`${pageData.baseURL}/api/set-theme/${key}`, {
+        method: "POST",
+    });
+
+    if (response.status != 200) {
+        alert("Failed to set theme: " + response.statusText);
+        return;
+    }
+    const newThemeStyle = await response.text();
+
+    const tempStyle = elem("style")
+        .html("* { transition: none !important; }")
+        .appendTo(document.head);
+
+    themeStyleElem.html(newThemeStyle);
+    document.documentElement.setAttribute("data-scheme", response.headers.get("X-Scheme"));
+    typeof onChanged == "function" && onChanged();
+    setTimeout(() => { tempStyle.remove(); }, 10);
+}
+
+function initThemeSwitcher() {
+    find(".mobile-navigation .theme-choices").replaceWith(
+        find(".header-container .theme-choices").cloneNode(true)
+    );
+
+    const presetElems = findAll(".theme-choices .theme-preset");
+    let themePreviewElems = document.getElementsByClassName("current-theme-preview");
+    let isLoading = false;
+
+    presetElems.forEach((presetElement) => {
+        const themeKey = presetElement.dataset.key;
+
+        if (themeKey === undefined) {
+            return;
+        }
+
+        if (themeKey == pageData.theme) {
+            presetElement.classList.add("current");
+        }
+
+        presetElement.addEventListener("click", () => {
+            if (themeKey == pageData.theme) return;
+            if (isLoading) return;
+
+            isLoading = true;
+            changeTheme(themeKey, function() {
+                isLoading = false;
+                pageData.theme = themeKey;
+                presetElems.forEach((e) => { e.classList.remove("current"); });
+
+                Array.from(themePreviewElems).forEach((preview) => {
+                    preview.querySelector(".theme-preset").replaceWith(
+                        presetElement.cloneNode(true)
+                    );
+                })
+
+                presetElems.forEach((e) => {
+                    if (e.dataset.key != themeKey) return;
+                    e.classList.add("current");
+                });
+            });
+        });
+    })
+}
+
 async function setupPage() {
+    initThemeSwitcher();
+
     const pageElement = document.getElementById("page");
     const pageContentElement = document.getElementById("page-content");
     const pageContent = await fetchPageContent(pageData);

internal/glance/static/js/masonry.js

@@ -37,9 +37,6 @@ export function setupMasonries() {
                 columnsFragment.append(column);
             }
 
-            // poor man's masonry
-            // TODO: add an option that allows placing items in the
-            // shortest column instead of iterating the columns in order
             for (let i = 0; i < items.length; i++) {
                 columnsFragment.children[i % columnsCount].appendChild(items[i]);
             }

internal/glance/static/js/popover.js

@@ -157,6 +157,9 @@ function hidePopover() {
 
     activeTarget.classList.remove("popover-active");
     containerElement.style.display = "none";
+    containerElement.style.removeProperty("top");
+    containerElement.style.removeProperty("left");
+    containerElement.style.removeProperty("right");
     document.removeEventListener("keydown", handleHidePopoverOnEscape);
     window.removeEventListener("resize", queueRepositionContainer);
     observer.unobserve(containerElement);
@@ -181,7 +184,12 @@ export function setupPopovers() {
     for (let i = 0; i < targets.length; i++) {
         const target = targets[i];
 
-        target.addEventListener("mouseenter", handleMouseEnter);
+        if (target.dataset.popoverTrigger === "click") {
+            target.addEventListener("click", handleMouseEnter);
+        } else {
+            target.addEventListener("mouseenter", handleMouseEnter);
+        }
+
         target.addEventListener("mouseleave", handleMouseLeave);
     }
 }

internal/glance/templates/document.html

@@ -1,9 +1,16 @@
 <!DOCTYPE html>
-<html {{ block "document-root-attrs" . }}{{ end }} lang="en" id="top">
+<html {{ block "document-root-attrs" . }}{{ end }} lang="en" id="top" data-scheme="{{ if .Request.Theme.Light }}light{{ else }}dark{{ end }}">
 <head>
     {{ block "document-head-before" . }}{{ end }}
+    <script>
+    if (navigator.platform === 'iPhone') document.documentElement.classList.add('ios');
+    const pageData = {
+        slug: "{{ .Page.Slug }}",
+        baseURL: "{{ .App.Config.Server.BaseURL }}",
+        theme: "{{ .Request.Theme.Key }}",
+    };
+    </script>
     <title>{{ block "document-title" . }}{{ end }}</title>
-    <script>if (navigator.platform === 'iPhone') document.documentElement.classList.add('ios');</script>
     <meta charset="UTF-8">
     <meta name="color-scheme" content="dark">
     <meta name="viewport" content="width=device-width, initial-scale=1.0, viewport-fit=cover">
@@ -11,12 +18,15 @@
     <meta name="mobile-web-app-capable" content="yes">
     <meta name="apple-mobile-web-app-status-bar-style" content="black-translucent">
     <meta name="apple-mobile-web-app-title" content="{{ .App.Config.Branding.AppName }}">
-    <meta name="theme-color" content="{{ .App.Config.Theme.BackgroundColorAsHex }}">
+    <meta name="theme-color" content="{{ .Request.Theme.BackgroundColorAsHex }}">
     <link rel="apple-touch-icon" sizes="512x512" href='{{ .App.Config.Branding.AppIconURL }}'>
     <link rel="manifest" href='{{ .App.VersionedAssetPath "manifest.json" }}'>
     <link rel="icon" type="image/png" href="{{ .App.Config.Branding.FaviconURL }}" />
     <link rel="stylesheet" href='{{ .App.StaticAssetPath "css/bundle.css" }}'>
     <script type="module" src='{{ .App.StaticAssetPath "js/main.js" }}'></script>
+    <style id="theme-style">
+    {{ .Request.Theme.CSS }}
+    </style>
     {{ block "document-head-after" . }}{{ end }}
 </head>
 <body>

internal/glance/templates/page.html

@@ -2,20 +2,7 @@
 
 {{ define "document-title" }}{{ .Page.Title }}{{ end }}
 
-{{ define "document-head-before" }}
-<script>
-    const pageData = {
-        slug: "{{ .Page.Slug }}",
-        baseURL: "{{ .App.Config.Server.BaseURL }}",
-    };
-</script>
-{{ end }}
-
-{{ define "document-root-attrs" }}class="{{ if .App.Config.Theme.Light }}light-scheme {{ end }}{{ if .Page.CenterVertically }}page-center-vertically{{ end }}"{{ end }}
-
 {{ define "document-head-after" }}
-{{ .App.ParsedThemeStyle }}
-
 {{ if ne "" .App.Config.Theme.CustomCSSFile }}
 <link rel="stylesheet" href="{{ .App.Config.Theme.CustomCSSFile }}?v={{ .App.CreatedAt.Unix }}">
 {{ end }}
@@ -36,9 +23,22 @@
         <div class="header flex padding-inline-widget widget-content-frame">
             <!-- TODO: Replace G with actual logo, first need an actual logo -->
             <div class="logo" aria-hidden="true">{{ if ne "" .App.Config.Branding.LogoURL }}<img src="{{ .App.Config.Branding.LogoURL }}" alt="">{{ else if ne "" .App.Config.Branding.LogoText }}{{ .App.Config.Branding.LogoText }}{{ else }}G{{ end }}</div>
-            <nav class="nav flex grow">
+            <nav class="nav flex grow hide-scrollbars">
                 {{ template "navigation-links" . }}
             </nav>
+            <div class="theme-picker self-center" data-popover-type="html" data-popover-position="below" data-popover-show-delay="0" data-popover-offset="0.7">
+                <div class="current-theme-preview">
+                    {{ .Request.Theme.PreviewHTML }}
+                </div>
+                <div data-popover-html>
+                    <div class="theme-choices">
+                        {{ .App.Config.Theme.PreviewHTML }}
+                        {{ range $_, $preset := .App.Config.Theme.Presets.Items }}
+                        {{ $preset.PreviewHTML }}
+                        {{ end }}
+                    </div>
+                </div>
+            </div>
         </div>
     </div>
     {{ end }}
@@ -49,15 +49,35 @@
             {{ range $i, $column := .Page.Columns }}
             <label class="mobile-navigation-label"><input type="radio" class="mobile-navigation-input" name="column" value="{{ $i }}" autocomplete="off"{{ if eq $i $.Page.PrimaryColumnIndex }} checked{{ end }}><div class="mobile-navigation-pill"></div></label>
             {{ end }}
-            <label class="mobile-navigation-label"><input type="checkbox" class="mobile-navigation-page-links-input" autocomplete="on"{{ if .Page.ExpandMobilePageNavigation }} checked{{ end }}><div class="hamburger-icon"></div></label>
+            <label class="mobile-navigation-label"><input type="checkbox" class="mobile-navigation-page-links-input" autocomplete="on"><div class="hamburger-icon"></div></label>
         </div>
-        <div class="mobile-navigation-page-links">
+
+        <div class="mobile-navigation-page-links hide-scrollbars">
             {{ template "navigation-links" . }}
         </div>
+
+        <div class="mobile-navigation-actions flex flex-column margin-block-10">
+            <div class="theme-picker flex justify-between items-center" data-popover-type="html" data-popover-position="above" data-popover-show-delay="0" data-popover-hide-delay="100" data-popover-anchor=".current-theme-preview" data-popover-trigger="click">
+                <div data-popover-html>
+                    <div class="theme-choices"></div>
+                </div>
+
+                <div class="size-h3 pointer-events-none">Change theme</div>
+
+                <div class="flex gap-15 items-center pointer-events-none">
+                    <div class="current-theme-preview">
+                        {{ .Request.Theme.PreviewHTML }}
+                    </div>
+                    <svg class="ui-icon" stroke="var(--color-text-subdue)" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="1.5">
+                        <path stroke-linecap="round" stroke-linejoin="round" d="M4.098 19.902a3.75 3.75 0 0 0 5.304 0l6.401-6.402M6.75 21A3.75 3.75 0 0 1 3 17.25V4.125C3 3.504 3.504 3 4.125 3h5.25c.621 0 1.125.504 1.125 1.125v4.072M6.75 21a3.75 3.75 0 0 0 3.75-3.75V8.197M6.75 21h13.125c.621 0 1.125-.504 1.125-1.125v-5.25c0-.621-.504-1.125-1.125-1.125h-4.072M10.5 8.197l2.88-2.88c.438-.439 1.15-.439 1.59 0l3.712 3.713c.44.44.44 1.152 0 1.59l-2.879 2.88M6.75 17.25h.008v.008H6.75v-.008Z" />
+                    </svg>
+                </div>
+            </div>
+        </div>
     </div>
 
     <div class="content-bounds grow{{ if ne "" .Page.Width }} content-bounds-{{ .Page.Width }} {{ end }}">
-        <main class="page" id="page" aria-live="polite" aria-busy="true">
+        <main class="page{{ if .Page.CenterVertically }} page-center-vertically{{ end }}" id="page" aria-live="polite" aria-busy="true">
             <h1 class="visually-hidden">{{ .Page.Title }}</h1>
             <div class="page-content" id="page-content"></div>
             <div class="page-loading-container">

internal/glance/templates/theme-preset-preview.html

@@ -0,0 +1,19 @@
+{{- $background := "hsl(240, 8%, 9%)" | safeCSS }}
+{{- $primary := "hsl(43, 50%, 70%)" | safeCSS  }}
+{{- $positive := "hsl(43, 50%, 70%)" | safeCSS }}
+{{- $negative := "hsl(0, 70%, 70%)" | safeCSS }}
+{{- if .BackgroundColor }}{{ $background = .BackgroundColor.String | safeCSS }}{{ end }}
+{{- if .PrimaryColor }}
+    {{- $primary = .PrimaryColor.String | safeCSS }}
+    {{- if not .PositiveColor }}
+        {{- $positive = $primary }}
+    {{- else }}
+        {{- $positive = .PositiveColor.String | safeCSS }}
+    {{- end }}
+{{- end }}
+{{- if .NegativeColor }}{{ $negative = .NegativeColor.String | safeCSS }}{{ end }}
+<button class="theme-preset{{ if .Light }} theme-preset-light{{ end }}" style="--color: {{ $background }}" data-key="{{ .Key }}">
+    <div class="theme-color" style="--color: {{ $primary }}"></div>
+    <div class="theme-color" style="--color: {{ $positive }}"></div>
+    <div class="theme-color" style="--color: {{ $negative }}"></div>
+</button>

internal/glance/templates/theme-style.gotmpl

@@ -1,9 +1,8 @@
-<style>
 :root {
     {{ if .BackgroundColor }}
-    --bgh: {{ .BackgroundColor.Hue }};
+    --bgh: {{ .BackgroundColor.H }};
-    --bgs: {{ .BackgroundColor.Saturation }}%;
+    --bgs: {{ .BackgroundColor.S }}%;
-    --bgl: {{ .BackgroundColor.Lightness }}%;
+    --bgl: {{ .BackgroundColor.L }}%;
     {{ end }}
     {{ if ne 0.0 .ContrastMultiplier }}--cm: {{ .ContrastMultiplier }};{{ end }}
     {{ if ne 0.0 .TextSaturationMultiplier }}--tsm: {{ .TextSaturationMultiplier }};{{ end }}
@@ -11,4 +10,3 @@
     {{ if .PositiveColor }}--color-positive: {{ .PositiveColor.String | safeCSS }};{{ end }}
     {{ if .NegativeColor }}--color-negative: {{ .NegativeColor.String | safeCSS }};{{ end }}
 }
-</style>

internal/glance/theme.go

@@ -0,0 +1,104 @@
+package glance
+
+import (
+	"fmt"
+	"html/template"
+	"net/http"
+)
+
+var (
+	themeStyleTemplate         = mustParseTemplate("theme-style.gotmpl")
+	themePresetPreviewTemplate = mustParseTemplate("theme-preset-preview.html")
+)
+
+func (a *application) handleThemeChangeRequest(w http.ResponseWriter, r *http.Request) {
+	themeKey := r.PathValue("key")
+
+	properties, exists := a.Config.Theme.Presets.Get(themeKey)
+	if !exists && themeKey != "default" {
+		w.WriteHeader(http.StatusNotFound)
+		return
+	}
+
+	if themeKey == "default" {
+		properties = &a.Config.Theme.themeProperties
+	}
+
+	http.SetCookie(w, &http.Cookie{
+		Name:  "theme",
+		Value: themeKey,
+		Path:  a.Config.Server.BaseURL + "/",
+	})
+
+	w.Header().Set("Content-Type", "text/css")
+	w.Header().Set("X-Scheme", ternary(properties.Light, "light", "dark"))
+	w.Write([]byte(properties.CSS))
+}
+
+type themeProperties struct {
+	BackgroundColor          *hslColorField `yaml:"background-color"`
+	PrimaryColor             *hslColorField `yaml:"primary-color"`
+	PositiveColor            *hslColorField `yaml:"positive-color"`
+	NegativeColor            *hslColorField `yaml:"negative-color"`
+	Light                    bool           `yaml:"light"`
+	ContrastMultiplier       float32        `yaml:"contrast-multiplier"`
+	TextSaturationMultiplier float32        `yaml:"text-saturation-multiplier"`
+
+	Key                  string        `yaml:"-"`
+	CSS                  template.CSS  `yaml:"-"`
+	PreviewHTML          template.HTML `yaml:"-"`
+	BackgroundColorAsHex string        `yaml:"-"`
+}
+
+func (t *themeProperties) init() error {
+	css, err := executeTemplateToString(themeStyleTemplate, t)
+	if err != nil {
+		return fmt.Errorf("compiling theme style: %v", err)
+	}
+	t.CSS = template.CSS(whitespaceAtBeginningOfLinePattern.ReplaceAllString(css, ""))
+
+	previewHTML, err := executeTemplateToString(themePresetPreviewTemplate, t)
+	if err != nil {
+		return fmt.Errorf("compiling theme preview: %v", err)
+	}
+	t.PreviewHTML = template.HTML(previewHTML)
+
+	if t.BackgroundColor != nil {
+		t.BackgroundColorAsHex = t.BackgroundColor.ToHex()
+	} else {
+		t.BackgroundColorAsHex = "#151519"
+	}
+
+	return nil
+}
+
+func (t1 *themeProperties) SameAs(t2 *themeProperties) bool {
+	if t1 == nil && t2 == nil {
+		return true
+	}
+	if t1 == nil || t2 == nil {
+		return false
+	}
+	if t1.Light != t2.Light {
+		return false
+	}
+	if t1.ContrastMultiplier != t2.ContrastMultiplier {
+		return false
+	}
+	if t1.TextSaturationMultiplier != t2.TextSaturationMultiplier {
+		return false
+	}
+	if !t1.BackgroundColor.SameAs(t2.BackgroundColor) {
+		return false
+	}
+	if !t1.PrimaryColor.SameAs(t2.PrimaryColor) {
+		return false
+	}
+	if !t1.PositiveColor.SameAs(t2.PositiveColor) {
+		return false
+	}
+	if !t1.NegativeColor.SameAs(t2.NegativeColor) {
+		return false
+	}
+	return true
+}

internal/glance/utils.go

@@ -15,6 +15,7 @@ import (
 )
 
 var sequentialWhitespacePattern = regexp.MustCompile(`\s+`)
+var whitespaceAtBeginningOfLinePattern = regexp.MustCompile(`(?m)^\s+`)
 
 func percentChange(current, previous float64) float64 {
 	return (current/previous - 1) * 100
@@ -149,15 +150,14 @@ func fileServerWithCache(fs http.FileSystem, cacheDuration time.Duration) http.H
 	})
 }
 
-func executeTemplateToHTML(t *template.Template, data interface{}) (template.HTML, error) {
+func executeTemplateToString(t *template.Template, data any) (string, error) {
 	var b bytes.Buffer
-
 	err := t.Execute(&b, data)
 	if err != nil {
 		return "", fmt.Errorf("executing template: %w", err)
 	}
 
-	return template.HTML(b.String()), nil
+	return b.String(), nil
 }
 
 func stringToBool(s string) bool {