From b6d3120086d8b5fda0e42b5fb05f719cb836da5c Mon Sep 17 00:00:00 2001
From: Daniel Imms <2193314+Tyriar@users.noreply.github.com>
Date: Thu, 1 Apr 2021 16:55:27 -0700
Subject: [PATCH] Restrict all sides of powerline glyphs

---
 .../src/atlas/WebglCharAtlas.ts               | 42 ++++++++++---------
 1 file changed, 23 insertions(+), 19 deletions(-)

diff --git a/addons/xterm-addon-webgl/src/atlas/WebglCharAtlas.ts b/addons/xterm-addon-webgl/src/atlas/WebglCharAtlas.ts
index 6a0f9a67..d368405b 100644
--- a/addons/xterm-addon-webgl/src/atlas/WebglCharAtlas.ts
+++ b/addons/xterm-addon-webgl/src/atlas/WebglCharAtlas.ts
@@ -367,7 +367,9 @@ export class WebglCharAtlas implements IDisposable {
       this._tmpCtx.globalAlpha = DIM_OPACITY;
     }
 
-    // Check if the char is a powerline glyph
+    // Check if the char is a powerline glyph, these will be restricted to a single cell glyph, no
+    // padding on either side that are allowed for other glyphs since they are designed to be pixel
+    // perfect but may render with "bad" anti-aliasing
     let isPowerlineGlyph = false;
     if (chars.length === 1) {
       const code = chars.charCodeAt(0);
@@ -403,7 +405,7 @@ export class WebglCharAtlas implements IDisposable {
       return NULL_RASTERIZED_GLYPH;
     }
 
-    const rasterizedGlyph = this._findGlyphBoundingBox(imageData, this._workBoundingBox, padding);
+    const rasterizedGlyph = this._findGlyphBoundingBox(imageData, this._workBoundingBox, isPowerlineGlyph);
     const clippedImageData = this._clipImageData(imageData, this._workBoundingBox);
 
     // Check if there is enough room in the current row and go to next if needed
@@ -436,12 +438,14 @@ export class WebglCharAtlas implements IDisposable {
    * @param imageData The image data to read.
    * @param boundingBox An IBoundingBox to put the clipped bounding box values.
    */
-  private _findGlyphBoundingBox(imageData: ImageData, boundingBox: IBoundingBox, padding: number): IRasterizedGlyph {
+  private _findGlyphBoundingBox(imageData: ImageData, boundingBox: IBoundingBox, restrictedGlyph: boolean): IRasterizedGlyph {
     boundingBox.top = 0;
+    const height = restrictedGlyph ? this._config.scaledCharHeight : this._tmpCanvas.height;
+    const width = restrictedGlyph ? this._config.scaledCharWidth : this._tmpCanvas.width;
     let found = false;
-    for (let y = 0; y < this._tmpCanvas.height; y++) {
-      for (let x = 0; x < this._tmpCanvas.width; x++) {
-        const alphaOffset = y * this._tmpCanvas.width * 4 + x * 4 + 3;
+    for (let y = 0; y < height; y++) {
+      for (let x = 0; x < width; x++) {
+        const alphaOffset = y * width * 4 + x * 4 + 3;
         if (imageData.data[alphaOffset] !== 0) {
           boundingBox.top = y;
           found = true;
@@ -454,9 +458,9 @@ export class WebglCharAtlas implements IDisposable {
     }
     boundingBox.left = 0;
     found = false;
-    for (let x = 0; x < this._tmpCanvas.width; x++) {
-      for (let y = 0; y < this._tmpCanvas.height; y++) {
-        const alphaOffset = y * this._tmpCanvas.width * 4 + x * 4 + 3;
+    for (let x = 0; x < width; x++) {
+      for (let y = 0; y < height; y++) {
+        const alphaOffset = y * width * 4 + x * 4 + 3;
         if (imageData.data[alphaOffset] !== 0) {
           boundingBox.left = x;
           found = true;
@@ -467,11 +471,11 @@ export class WebglCharAtlas implements IDisposable {
         break;
       }
     }
-    boundingBox.right = this._tmpCanvas.width;
+    boundingBox.right = width;
     found = false;
-    for (let x = this._tmpCanvas.width - 1; x >= 0; x--) {
-      for (let y = 0; y < this._tmpCanvas.height; y++) {
-        const alphaOffset = y * this._tmpCanvas.width * 4 + x * 4 + 3;
+    for (let x = width - 1; x >= 0; x--) {
+      for (let y = 0; y < height; y++) {
+        const alphaOffset = y * width * 4 + x * 4 + 3;
         if (imageData.data[alphaOffset] !== 0) {
           boundingBox.right = x;
           found = true;
@@ -482,11 +486,11 @@ export class WebglCharAtlas implements IDisposable {
         break;
       }
     }
-    boundingBox.bottom = this._tmpCanvas.height;
+    boundingBox.bottom = height;
     found = false;
-    for (let y = this._tmpCanvas.height - 1; y >= 0; y--) {
-      for (let x = 0; x < this._tmpCanvas.width; x++) {
-        const alphaOffset = y * this._tmpCanvas.width * 4 + x * 4 + 3;
+    for (let y = height - 1; y >= 0; y--) {
+      for (let x = 0; x < width; x++) {
+        const alphaOffset = y * width * 4 + x * 4 + 3;
         if (imageData.data[alphaOffset] !== 0) {
           boundingBox.bottom = y;
           found = true;
@@ -509,8 +513,8 @@ export class WebglCharAtlas implements IDisposable {
         y: (boundingBox.bottom - boundingBox.top + 1) / TEXTURE_HEIGHT
       },
       offset: {
-        x: -boundingBox.left + padding,
-        y: -boundingBox.top + padding
+        x: -boundingBox.left + (restrictedGlyph ? TMP_CANVAS_GLYPH_PADDING : 0),
+        y: -boundingBox.top + (restrictedGlyph ? TMP_CANVAS_GLYPH_PADDING : 0)
       }
     };
   }