Theme switch button

src/common/di.config.ts

@@ -19,6 +19,7 @@ import { FitToScreenKeyListener as CenterDiagramKeyListener } from "./fitToScree
 import { DiagramModificationCommandStack } from "./customCommandStack";
 
 import "./commonStyling.css";
+import { LightDarkSwitch } from "./lightDarkSwitch";
 
 export const commonModule = new ContainerModule((bind, unbind, isBound, rebind) => {
     bind(ServerCommandPaletteActionProvider).toSelf().inSingletonScope();
@@ -33,6 +34,10 @@ export const commonModule = new ContainerModule((bind, unbind, isBound, rebind)
     bind(TYPES.IUIExtension).toService(HelpUI);
     bind(EDITOR_TYPES.DefaultUIElement).toService(HelpUI);
 
+    bind(LightDarkSwitch).toSelf().inSingletonScope();
+    bind(TYPES.IUIExtension).toService(LightDarkSwitch);
+    bind(EDITOR_TYPES.DefaultUIElement).toService(LightDarkSwitch);
+
     bind(DynamicChildrenProcessor).toSelf().inSingletonScope();
 
     unbind(TYPES.ICommandStack);

src/common/lightDarkSwitch.css

@@ -0,0 +1,20 @@
+div.light-dark-switch {
+    left: 20px;
+    bottom: 70px;
+    padding: 10px 10px;
+}
+
+#light-dark-label #light-dark-button::before {
+    content: "";
+    background-image: url("@fortawesome/fontawesome-free/svgs/regular/moon.svg");
+    display: inline-block;
+    filter: invert(var(--dark-mode));
+    height: 16px;
+    width: 16px;
+    background-size: 16px 16px;
+    vertical-align: text-top;
+}
+
+#light-dark-switch:checked ~ label #light-dark-button::before {
+    background-image: url("@fortawesome/fontawesome-free/svgs/regular/sun.svg");
+}

src/common/lightDarkSwitch.ts

@@ -0,0 +1,45 @@
+import { injectable } from "inversify";
+import "./lightDarkSwitch.css";
+import { AbstractUIExtension } from "sprotty";
+
+@injectable()
+export class LightDarkSwitch extends AbstractUIExtension {
+    static readonly ID = "light-dark-switch";
+    static useDarkMode = false;
+
+    id(): string {
+        return LightDarkSwitch.ID;
+    }
+    containerClass(): string {
+        return LightDarkSwitch.ID;
+    }
+    protected initializeContents(containerElement: HTMLElement): void {
+        containerElement.classList.add("ui-float");
+        containerElement.innerHTML = `
+          <input type="checkbox" id="light-dark-switch" hidden />
+          <label id="light-dark-label" for="light-dark-switch">
+            <div id="light-dark-button"></div>
+          </label>
+      `;
+
+        const checkbox = containerElement.querySelector("#light-dark-switch") as HTMLInputElement;
+        checkbox.addEventListener("change", () => {
+            this.changeDarkMode(checkbox.checked);
+        });
+
+        // use the default browser theme
+        if (window.matchMedia && window.matchMedia("(prefers-color-scheme: dark)").matches) {
+            checkbox.checked = true;
+            this.changeDarkMode(true);
+        }
+    }
+
+    private changeDarkMode(useDark: boolean) {
+        const rootElement = document.querySelector(":root") as HTMLElement;
+        const sprottyElement = document.querySelector("#sprotty") as HTMLElement;
+
+        const value = useDark ? "dark" : "light";
+        rootElement.setAttribute("data-theme", value);
+        sprottyElement.setAttribute("data-theme", value);
+    }
+}

src/theme.css

@@ -9,19 +9,17 @@
     --dark-mode: 0;
 }
 
-@media (prefers-color-scheme: dark) {
-    :root {
-        --color-foreground: #fff;
-        --color-background: #000;
-        --color-primary: #222;
-        --color-valid: #0f0;
-        --color-tool-palette-hover: #444;
-        --color-tool-palette-selected: #555;
-        --dark-mode: 1;
-    }
+:root[data-theme="dark"] {
+    --color-foreground: #fff;
+    --color-background: #000;
+    --color-primary: #222;
+    --color-valid: #0f0;
+    --color-tool-palette-hover: #444;
+    --color-tool-palette-selected: #555;
+    --dark-mode: 1;
+}
 
-    #sprotty div {
-        /* Use default dark theme browser styles for scrollbars etc. inside all UI extensions */
-        color-scheme: dark;
-    }
+#sprotty[data-theme="dark"] div {
+    /* Use default dark theme browser styles for scrollbars etc. inside all UI extensions */
+    color-scheme: dark;
 }