add brush preview

static/base.css

@@ -26,6 +26,10 @@ body {
     line-height: var(--line-height);
 }
 
+* {
+    box-sizing: border-box;
+}
+
 /* Fonts */
 
 :root {

static/brush-editor.js

@@ -1,4 +1,5 @@
 import { CodeEditor, getLineStart } from "rkgk/code-editor.js";
+import { BrushPreview } from "rkgk/brush-preview.js";
 
 const defaultBrush = `
 -- This is your brush.

static/brush-preview.js

@@ -0,0 +1,57 @@
+import { Pixmap } from "rkgk/haku.js";
+
+export class BrushPreview extends HTMLElement {
+    constructor() {
+        super();
+    }
+
+    connectedCallback() {
+        this.canvas = this.appendChild(document.createElement("canvas"));
+        this.ctx = this.canvas.getContext("2d");
+        this.#resizeCanvas();
+    }
+
+    #resizeCanvas() {
+        this.canvas.width = this.clientWidth;
+        this.canvas.height = this.clientHeight;
+
+        if (this.pixmap != null) {
+            this.pixmap.destroy();
+        }
+        this.pixmap = new Pixmap(this.canvas.width, this.canvas.height);
+    }
+
+    #renderBrushInner(haku) {
+        haku.resetVm();
+
+        let evalResult = haku.evalBrush();
+        if (evalResult.status != "ok") {
+            return { status: "error", phase: "eval", result: evalResult };
+        }
+
+        this.pixmap.clear();
+        let renderResult = haku.renderValue(
+            this.pixmap,
+            this.canvas.width / 2,
+            this.canvas.height / 2,
+        );
+        if (renderResult.status != "ok") {
+            return { status: "error", phase: "render", result: renderResult };
+        }
+
+        this.ctx.putImageData(this.pixmap.getImageData(), 0, 0);
+
+        return { status: "ok" };
+    }
+
+    renderBrush(haku) {
+        this.classList.remove("error");
+        let result = this.#renderBrushInner(haku);
+        if (result.status == "error") {
+            this.classList.add("error");
+        }
+        return result;
+    }
+}
+
+customElements.define("rkgk-brush-preview", BrushPreview);

static/index.css

@@ -32,7 +32,7 @@ main {
         padding: 16px;
 
         display: grid;
-        grid-template-columns: [left] 1fr [right-resize] auto [right] var(--right-width);
+        grid-template-columns: [left] 1fr [right-resize] auto [right] minmax(0, var(--right-width));
 
         /* Pass all events through. Children may receive events as normal. */
         pointer-events: none;
@@ -43,23 +43,34 @@ main {
 
         &>.right {
             grid-column: right / right;
-            height: fit-content;
             min-height: 0;
-            max-height: 100%;
 
-            display: flex;
-            flex-direction: row;
-            justify-content: stretch;
+            display: grid;
+            grid-template-rows: minmax(0, min-content);
+            grid-template-columns: [floating] max-content [resize] min-content [docked] auto;
 
-            &>rkgk-resize-handle {
-                flex-shrink: 0;
-                height: auto;
+            padding-left: 16px;
+
+            pointer-events: none;
+
+            &>* {
+                min-width: 0;
+                min-height: 0;
             }
 
-            &>rkgk-brush-editor {
-                height: auto;
-                overflow: auto;
-                flex-grow: 1;
+            &>rkgk-resize-handle {
+                pointer-events: auto;
+            }
+
+            &>.docked>rkgk-brush-editor {
+                max-height: 100%;
+                pointer-events: auto;
+            }
+
+            &>.floating>rkgk-brush-preview {
+                width: 128px;
+                height: 128px;
+                pointer-events: auto;
             }
         }
     }
@@ -175,6 +186,8 @@ rkgk-code-editor {
     position: relative;
     width: 100%;
 
+    overflow: auto;
+
     &>.layer {
         position: absolute;
         left: 0;
@@ -259,14 +272,29 @@ rkgk-code-editor {
         resize: none;
         white-space: pre-wrap;
         border: none;
+
+        &:focus {
+            outline: none;
+        }
+    }
+
+    &:has(textarea:focus) {
+        outline: 1px solid var(--color-brand-blue);
+        outline-offset: 4px;
     }
 }
 
 /* Brush editor */
 
-rkgk-brush-editor {
+rkgk-brush-editor.rkgk-panel {
     padding: 12px;
 
+    display: flex;
+    flex-direction: column;
+    gap: 4px;
+
+    position: relative;
+    
     &>.text-area {
         display: block;
         width: 100%;
@@ -283,8 +311,8 @@ rkgk-brush-editor {
     }
 
     &>.error-header {
-        margin-top: 1em;
-        margin-bottom: 0;
+        margin: 0;
+        margin-top: 0.5em;
         font-size: 1rem;
         color: var(--color-error);
     }
@@ -296,6 +324,36 @@ rkgk-brush-editor {
     }
 }
 
+/* Brush preview */
+
+rkgk-brush-preview {
+    --checkerboard-light: #f2f2f2;
+    --checkerboard-dark: #e1e1e1;
+    --checkerboard-size: 64px;
+
+    display: block;
+    position: relative;
+
+    background:
+        repeating-conic-gradient(var(--checkerboard-light) 0% 25%, var(--checkerboard-dark) 0% 50%)
+        50% 50% / var(--checkerboard-size) var(--checkerboard-size);
+    border-radius: 4px;
+
+    &.error {
+        &>canvas {
+            display: none;
+        }
+
+        &::before {
+            content: "(error)";
+            position: absolute;
+            left: 50%;
+            top: 50%;
+            transform: translate(-50%, -50%);
+        }
+    }
+}
+
 /* Welcome screen */
 
 rkgk-welcome {
@@ -359,7 +417,8 @@ rkgk-connection-status {
         }
 
         &.icon {
-            padding: 4px 4px;
+            width: 24px;
+            height: 24px;
         }
 
         &:first-child {

static/index.js

@@ -16,6 +16,7 @@ let main = document.querySelector("main");
 let canvasRenderer = main.querySelector("rkgk-canvas-renderer");
 let reticleRenderer = main.querySelector("rkgk-reticle-renderer");
 let brushEditor = main.querySelector("rkgk-brush-editor");
+let brushPreview = main.querySelector("rkgk-brush-preview");
 let welcome = main.querySelector("rkgk-welcome");
 let connectionStatus = main.querySelector("rkgk-connection-status");
 
@@ -260,10 +261,25 @@ function readUrl(urlString) {
         updateUrl(session, canvasRenderer.viewport),
     );
 
-    brushEditor.renderHakuResult("Compilation", currentUser.setBrush(brushEditor.code));
+    function compileBrush() {
+        let compileResult = currentUser.setBrush(brushEditor.code);
+        brushEditor.renderHakuResult("Compilation", compileResult);
+
+        if (compileResult.status != "ok") return;
+
+        let previewResult = brushPreview.renderBrush(currentUser.haku);
+        if (previewResult.status == "error") {
+            brushEditor.renderHakuResult(
+                previewResult.phase == "eval" ? "Evaluation" : "Rendering",
+                previewResult.result,
+            );
+        }
+    }
+
+    compileBrush();
     brushEditor.addEventListener(".codeChanged", async () => {
         flushPlotQueue();
-        brushEditor.renderHakuResult("Compilation", currentUser.setBrush(brushEditor.code));
+        compileBrush();
         session.sendSetBrush(brushEditor.code);
     });
 

static/resize-handle.js

@@ -47,6 +47,7 @@ export class ResizeHandle extends HTMLElement {
             let mouseDown = await listen([this, "mousedown"]);
             let startingSize = this.size;
             if (mouseDown.button == 0) {
+                mouseDown.preventDefault();
                 this.classList.add("dragging");
 
                 while (true) {

template/index.hbs.html

@@ -22,6 +22,7 @@
             import "rkgk/live-reload.js";
 
             import "rkgk/brush-editor.js";
+            import "rkgk/brush-preview.js";
             import "rkgk/canvas-renderer.js";
             import "rkgk/connection-status.js";
             import "rkgk/framework.js";
@@ -59,14 +60,20 @@
                     <hr>
                     <a href="/docs/rkgk.html">Manual</a>
                 </div>
+
                 <div class="right">
+                    <div class="floating">
+                        <rkgk-brush-preview></rkgk-brush-preview>
+                    </div>
                     <rkgk-resize-handle
                         data-direction="vertical"
                         data-target="panels-overlay"
                         data-target-property="--right-width"
-                        data-init-size="384"
-                        data-min-size="128"></rkgk-resize-handle>
-                    <rkgk-brush-editor></rkgk-brush-editor>
+                        data-init-size="512"
+                        data-min-size="384"></rkgk-resize-handle>
+                    <div class="docked">
+                        <rkgk-brush-editor></rkgk-brush-editor>
+                    </div>
                 </div>
             </div>