From e6a28635f81e4f12af2c9b9f9c5c38a31ca3468b Mon Sep 17 00:00:00 2001
From: kts of kettek <kts@kettek.net>
Date: Fri, 16 Feb 2024 12:08:35 -0800
Subject: [PATCH] Implement brush movement interpolation

---
 frontend/src/types/tools.ts | 57 ++++++++++++++++++++++++-------------
 1 file changed, 38 insertions(+), 19 deletions(-)

diff --git a/frontend/src/types/tools.ts b/frontend/src/types/tools.ts
index 86eeb24..5a90cfc 100644
--- a/frontend/src/types/tools.ts
+++ b/frontend/src/types/tools.ts
@@ -40,12 +40,18 @@ export interface PickerToolContext {
 }
 
 export class BrushTool implements Tool {
+  private lastX: number
+  private lastY: number
   private active: boolean
   isActive(): boolean {
     return this.active
   }
 
   pointerDown(ctx: ToolContext & BrushToolContext, ptr: Pointer) {
+    // Store last for interp.
+    this.lastX = ptr.x
+    this.lastY = ptr.y
+
     this.active = true
     ctx.file.capture()
     if (ctx.brushSize == 1) {
@@ -73,28 +79,41 @@ export class BrushTool implements Tool {
     }
   }
   pointerMove(ctx: ToolContext & BrushToolContext, ptr: Pointer) {
-    if (ctx.brushSize == 1) {
-      let p = ctx.file.canvas.getPixel(ptr.x, ptr.y)
-      if (p !== -1) {
-        ctx.file.push(new PixelPlaceUndoable(ptr.x, ptr.y, p, ctx.colorIndex))
-      }
-    } else if (ctx.brushSize == 2) {
-      for (let x1 = 0; x1 < 2; x1++) {
-        for (let y1 = 0; y1 < 2; y1++) {
-          let p = ctx.file.canvas.getPixel(ptr.x+x1, ptr.y+y1)
-          if (p !== -1) {
-            ctx.file.push(new PixelPlaceUndoable(ptr.x+x1, ptr.y+y1, p, ctx.colorIndex))
+    let dx = this.lastX - ptr.x
+    let dy = this.lastY - ptr.y
+    this.lastX = ptr.x
+    this.lastY = ptr.y
+
+    let angle = Math.atan2(dy, dx)
+    let dist = Math.sqrt(dx*dx + dy*dy)
+    let steps = Math.ceil(dist)
+    for (let i = 0; i < steps; i++) {
+      let x = Math.floor(this.lastX + Math.cos(angle) * i)
+      let y = Math.floor(this.lastY + Math.sin(angle) * i)
+
+      if (ctx.brushSize == 1) {
+        let p = ctx.file.canvas.getPixel(x, y)
+        if (p !== -1) {
+          ctx.file.push(new PixelPlaceUndoable(x, y, p, ctx.colorIndex))
+        }
+      } else if (ctx.brushSize == 2) {
+        for (let x1 = 0; x1 < 2; x1++) {
+          for (let y1 = 0; y1 < 2; y1++) {
+            let p = ctx.file.canvas.getPixel(x+x1, y+y1)
+            if (p !== -1) {
+              ctx.file.push(new PixelPlaceUndoable(x+x1, y+y1, p, ctx.colorIndex))
+            }
           }
         }
+      } else {
+        let shape: PixelPosition[]
+        if (ctx.brushType == "circle") {
+          shape = FilledCircle(x, y, ctx.brushSize-2, ctx.colorIndex)
+        } else if (ctx.brushType == "square") {
+          shape = FilledSquare(x, y, ctx.brushSize, ctx.colorIndex)
+        }
+        ctx.file.push(new PixelsPlaceUndoable(shape))
       }
-    } else {
-      let shape: PixelPosition[]
-      if (ctx.brushType == "circle") {
-        shape = FilledCircle(ptr.x, ptr.y, ctx.brushSize-2, ctx.colorIndex)
-      } else if (ctx.brushType == "square") {
-        shape = FilledSquare(ptr.x, ptr.y, ctx.brushSize, ctx.colorIndex)
-      }
-      ctx.file.push(new PixelsPlaceUndoable(shape))
     }
   }
   pointerUp(ctx: ToolContext, ptr: Pointer) {