Draw grid points in batches

1 files changed, 23 insertions, 9 deletions

diff --git a/src/diagramdocument.cpp b/src/diagramdocument.cpp
index 32b492e..d41ecdc 100644
--- a/src/diagramdocument.cpp
+++ b/src/diagramdocument.cpp
@@ -93,19 +93,33 @@ DiagramDocument::setGridColor(const QColor &color)
 void
 DiagramDocument::drawBackground(QPainter *painter, const QRectF &rect)
 {
+	const int pointBufferSize = 5000;
+	static QPoint pointBuffer[pointBufferSize];
 	if (!d->printing && d->gridVisible) {
-		qreal gridSize = d->gridSize;
-		qreal x0 = gridSize * floor(rect.left() / gridSize);
-		qreal y0 = gridSize * floor(rect.top() / gridSize);
-		qreal x1 = gridSize * ceil(rect.right() / gridSize);
-		qreal y1 = gridSize * ceil(rect.bottom() / gridSize);
+		int gridSize = d->gridSize;
+		int x0 = gridSize * floor(rect.left() / gridSize);
+		int y0 = gridSize * floor(rect.top() / gridSize);
+		int x1 = gridSize * ceil(rect.right() / gridSize);
+		int y1 = gridSize * ceil(rect.bottom() / gridSize);
 		painter->save();
 		painter->setPen(d->gridPen);
 		painter->setRenderHint(QPainter::Antialiasing, false);
-		// FIXME do this in one QPainter::drawPoints call
-		for (qreal x = x0; x < x1; x += gridSize)
-			for (qreal y = y0; y < y1; y += gridSize)
-				painter->drawPoint(x, y);
+		int pointsUsed = 0;
+		for (int x = x0; x < x1; x += gridSize) {
+			for (int y = y0; y < y1; y += gridSize) {
+				pointBuffer[pointsUsed].setX(x);
+				pointBuffer[pointsUsed].setY(y);
+				pointsUsed++;
+				if (pointsUsed == pointBufferSize) {
+					painter->drawPoints(pointBuffer, pointsUsed);
+					pointsUsed = 0;
+				}
+			}
+		}
+		if (pointsUsed > 0) {
+			painter->drawPoints(pointBuffer, pointsUsed);
+			pointsUsed = 0;
+		}
 		painter->restore();
 	}
 }