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fix: clear canvas before filling to support transparent backgrounds #116

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fix: clear canvas before filling to support transparent backgrounds #116

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ee0e944
fix: clear canvas before filling to support transparent backgrounds
slang25 Jan 10, 2026
79e3734
style: remove extra blank line
slang25 Jan 13, 2026
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12 changes: 10 additions & 2 deletions lib/renderer.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -515,12 +515,16 @@ export class CanvasRenderer {
*/
private renderLine(line: GhosttyCell[], y: number, cols: number): void {
const lineY = y * this.metrics.height;
const lineWidth = cols * this.metrics.width;

// Clear line background with theme color.
// Clear line background then fill with theme color.
// We clear just the cell area - glyph overflow is handled by also
// redrawing adjacent rows (see render() method).
// clearRect is needed because fillRect composites rather than replaces,
// so transparent/translucent backgrounds wouldn't clear previous content.
this.ctx.clearRect(0, lineY, lineWidth, this.metrics.height);
this.ctx.fillStyle = this.theme.background;
this.ctx.fillRect(0, lineY, cols * this.metrics.width, this.metrics.height);
this.ctx.fillRect(0, lineY, lineWidth, this.metrics.height);

// PASS 1: Draw all cell backgrounds first
// This ensures all backgrounds are painted before any text, allowing text
Expand Down Expand Up @@ -854,6 +858,7 @@ export class CanvasRenderer {
const scrollbarTrackHeight = canvasHeight - scrollbarPadding * 2;

// Always clear the scrollbar area first (fixes ghosting when fading out)
ctx.clearRect(scrollbarX - 2, 0, scrollbarWidth + 6, canvasHeight);
ctx.fillStyle = this.theme.background;
ctx.fillRect(scrollbarX - 2, 0, scrollbarWidth + 6, canvasHeight);

Expand Down Expand Up @@ -966,6 +971,9 @@ export class CanvasRenderer {
* Clear entire canvas
*/
public clear(): void {
// clearRect first because fillRect composites rather than replaces,
// so transparent/translucent backgrounds wouldn't clear previous content.
this.ctx.clearRect(0, 0, this.canvas.width, this.canvas.height);
this.ctx.fillStyle = this.theme.background;
this.ctx.fillRect(0, 0, this.canvas.width, this.canvas.height);
}
Expand Down