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snap repaint clear/fill to integer pixels to kill seam bars

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cellWidth is fractional, so in repaintColumns the clearRect cleared a run's
edge pixel to full transparency while the background fillRect covered that same
pixel only partially (antialiased), leaving a ~1px part-transparent column that
showed the near-black pane background as a thin bar 1-2 cells before the cursor.
Full-row repaint hid it because the highlighted line is then one contiguous
fill with no internal junction.

Route the clear and the background fills through a shared columnX() that rounds
each column boundary to a whole device pixel, so run edges land on integer
pixels with full single coverage and adjacent runs tile seamlessly.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Gregor Lohaus
2026-05-31 21:56:01 +02:00
parent 5728733f5f
commit 6613f1f746
1 changed files with 15 additions and 6 deletions
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21
src/main/java/com/gregor/jprototerm/TerminalPaneNode.java
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@@ -825,6 +825,14 @@ final class TerminalPaneNode extends Region {
return Math.ceil(TerminalMetrics.PADDING + (row + 1) * metrics.lineHeight());
}
// Left edge of a column, snapped to a whole device pixel. Both the clearRect and the
// background fillRect go through this so a run's edges land on integer pixels: at a
// fractional boundary clearRect clears the edge pixel fully while fillRect would only
// cover it partially, leaving a thin transparent (black) seam through the line.
private double columnX(int column) {
return Math.round(TerminalMetrics.PADDING + column * metrics.cellWidth());
}
private void repaintColumns(GraphicsContext gc, RenderRow row, int startColumn, int endColumn) {
if (endColumn < startColumn) {
return;
@@ -836,8 +844,8 @@ final class TerminalPaneNode extends Region {
double contentTop = TerminalMetrics.PADDING + row.row() * lineHeight;
double localCellTop = contentTop - rowTop;
double baseline = TerminalMetrics.PADDING + metrics.baselineOffset() + row.row() * lineHeight - rowTop;
double x = TerminalMetrics.PADDING + startColumn * cellWidth;
double width = (endColumn - startColumn + 1) * cellWidth;
double x = columnX(startColumn);
double width = columnX(endColumn + 1) - x;
gc.clearRect(x, 0.0, width, canvas.getHeight());
if (startColumn == 0) {
@@ -845,7 +853,7 @@ final class TerminalPaneNode extends Region {
gc.fillRect(0.0, 0.0, TerminalMetrics.PADDING, canvas.getHeight());
}
if (endColumn >= row.cells().size() - 1) {
double contentRight = TerminalMetrics.PADDING + row.cells().size() * cellWidth;
double contentRight = columnX(row.cells().size());
gc.setFill(rowEdgeBackground(row, false));
gc.fillRect(contentRight, 0.0, canvas.getWidth() - contentRight, canvas.getHeight());
}
@@ -860,7 +868,7 @@ final class TerminalPaneNode extends Region {
return;
}
double contentLeft = TerminalMetrics.PADDING;
double contentRight = contentLeft + columns * metrics.cellWidth();
double contentRight = columnX(columns);
gc.setFill(rowEdgeBackground(row, true));
gc.fillRect(0.0, 0.0, contentLeft, bandHeight);
gc.setFill(rowEdgeBackground(row, false));
@@ -914,11 +922,12 @@ final class TerminalPaneNode extends Region {
if (background == null || endColumn < startColumn) {
return;
}
double left = columnX(startColumn);
gc.setFill(background);
gc.fillRect(
TerminalMetrics.PADDING + startColumn * cellWidth,
left,
localCellTop,
(endColumn - startColumn + 1) * cellWidth,
columnX(endColumn + 1) - left,
lineHeight);
}