From a31d8dd81b16d7df1e064105458e1dc37abafdd7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Emre=20Ak=C4=B1?= <aki.emre@icloud.com>
Date: Sat, 4 Nov 2023 03:57:09 +0300
Subject: [PATCH] fix(r_draw): implement double-buffering and optimize frame
 flushing

  * add "true" double-buffering and set a pristine framebuffer on
    each flush call, instead of diligently painting the entire
    `<canvas />` black
---
 src/engine/r_draw.ts | 24 +++++++++---------------
 src/game/g_run.ts    |  7 +------
 src/typedef.d.ts     |  8 ++------
 3 files changed, 12 insertions(+), 27 deletions(-)

diff --git a/src/engine/r_draw.ts b/src/engine/r_draw.ts
index ba4b9d3..88c0ca1 100644
--- a/src/engine/r_draw.ts
+++ b/src/engine/r_draw.ts
@@ -26,32 +26,28 @@
     const R_FlushBuffer = R_Screen.R_FlushBuffer;
     const R_InitBuffer = R_Screen.R_InitBuffer;
 
-    let frameBuffer: ImageData;
+    /* double-buffering */
+    let frameBuffer: ImageData, cleanFrameBuffer: Uint8ClampedArray;
     let zBuffer: Float32Array, cleanZBuffer: Float32Array;
 
     function R_InitFrameBuffer (): void
     {
+        const frameBufferSize = N_PIXELS << 2;
+        cleanFrameBuffer = new Uint8ClampedArray(frameBufferSize);
+        for (let i = 3; i < frameBufferSize; i += 4) cleanFrameBuffer[i] = 255;
         frameBuffer = R_InitBuffer(SCREEN_W, SCREEN_H);
     }
 
-    function R_ResetFrameBuffer (): void
-    {
-        R_FillRect(0, 0, SCREEN_W, SCREEN_H, 0, 0, 0, 255);
-    }
-
-    function R_FlushFrame (): void
-    {
-        R_FlushBuffer(frameBuffer);
-    }
-
     function R_InitZBuffer (): void
     {
         cleanZBuffer = new Float32Array(N_PIXELS);
         zBuffer = new Float32Array(N_PIXELS);
     }
 
-    function R_ResetZBuffer (): void
+    function R_FlushFrame (): void
     {
+        R_FlushBuffer(frameBuffer);
+        frameBuffer.data.set(cleanFrameBuffer);
         zBuffer.set(cleanZBuffer);
     }
 
@@ -1024,10 +1020,8 @@
     {
         return {
             R_InitFrameBuffer,
-            R_ResetFrameBuffer,
-            R_FlushFrame,
             R_InitZBuffer,
-            R_ResetZBuffer,
+            R_FlushFrame,
             R_FillRect,
             R_DrawLine,
             R_DrawLine_DDA,
diff --git a/src/game/g_run.ts b/src/game/g_run.ts
index ea8565d..6103ccc 100644
--- a/src/game/g_run.ts
+++ b/src/game/g_run.ts
@@ -31,9 +31,7 @@
     const R_DebugStats = R_Camera.R_DebugStats;
 
     const R_Draw = __import__R_Draw();
-    const R_ResetFrameBuffer = R_Draw.R_ResetFrameBuffer;
     const R_FlushFrame = R_Draw.R_FlushFrame;
-    const R_ResetZBuffer = R_Draw.R_ResetZBuffer;
 
     const R_Drawers = __import__R_Drawers();
     const R_TitleDrawer = R_Drawers.R_TitleDrawer;
@@ -53,9 +51,6 @@
 
     function G_UpdateScreen (deltaT: number): void
     {
-        // clear the frame buffer so that the frame can start fresh
-        R_ResetFrameBuffer();
-        R_ResetZBuffer();
         R_ChangeRenderMode();
         R_RenderGeometries(nTrisOnScreen);
         R_FlushFrame();
@@ -100,7 +95,7 @@
     {
         if (!setupResolution) return; // exit with error
         // first, clear the frame buffer for any further drawing to take place
-        R_ResetFrameBuffer();
+        R_FlushFrame();
         // then, clear the loading animation that is currently running
         AN_CancelAnimation(setupResolution.loadingId);
         /* finally, start the animation for the title screen */
diff --git a/src/typedef.d.ts b/src/typedef.d.ts
index 0d87566..2a2eb71 100644
--- a/src/typedef.d.ts
+++ b/src/typedef.d.ts
@@ -432,10 +432,8 @@ declare function __import__R_Camera (): __Mod__R_Camera;
 // engine/r_draw.ts
 // -----------------------------------------------------------------------------
 type R_InitFrameBuffer = () => void;
-type R_ResetFrameBuffer = () => void;
-type R_FlushFrame = () => void;
 type R_InitZBuffer = () => void;
-type R_ResetZBuffer = () => void;
+type R_FlushFrame = () => void;
 
 type R_FillRect = (
     x: number, y: number,
@@ -535,10 +533,8 @@ type R_Print = (
 
 type __Mod__R_Draw = {
     R_InitFrameBuffer: R_InitFrameBuffer,
-    R_ResetFrameBuffer: R_ResetFrameBuffer,
-    R_FlushFrame: R_FlushFrame,
     R_InitZBuffer: R_InitZBuffer,
-    R_ResetZBuffer: R_ResetZBuffer,
+    R_FlushFrame: R_FlushFrame,
     R_FillRect: R_FillRect,
     R_DrawLine: R_DrawLine,
     R_DrawLine_DDA: R_DrawLine_DDA,