[GTK] Performance of TextLayout.getBounds() is very bad for long text [EBZ#551588] ---------------------------------------------------------------------------------- Key: ERT-762 URL: https://issues.jboss.org/browse/ERT-762 Project: Eclipse Release Train Issue Type: Task Components: Platform Reporter: Friendly Jira Robot Assignee: Eric Williams Priority: Major Labels: 4.14_M1, SWT, bzira I've noticed a slow performance of TextLayout.getBounds() method on Linux. The profiler shows an excessive amount of calls to OS.pango_layout_get_line_count(layout) method. Looking through the code I'm noticing that this is due to the bad design in TextLayout class, as it repeats calls to same OS methods repeatedly in a loop. The TextLayout.getBounds() method looks like this: public Rectangle getBounds() { checkLayout(); Rectangle bounds = DPIUtil.autoScaleDown(getDevice(), getBoundsInPixels()); int lineCount = OS.pango_layout_get_line_count(layout); int totalLineheight = getScaledVerticalIndent(); for (int i = 0; i < lineCount; i++) { totalLineheight += this.getLineBounds(i).height + OS.PANGO_PIXELS(OS.pango_layout_get_spacing(layout)); } bounds.height = totalLineheight; return bounds; } Here I believe the result of OS.pango_layout_get_spacing(layout) could be cached. Further down the line this calls TextLayout.getLineBoundsInPixels method. Rectangle getLineBoundsInPixels(int lineIndex) { computeRuns(); int lineCount = OS.pango_layout_get_line_count(layout); if (!(0 <= lineIndex && lineIndex < lineCount)) SWT.error(SWT.ERROR_INVALID_RANGE); long iter = OS.pango_layout_get_iter(layout); if (iter == 0) SWT.error(SWT.ERROR_NO_HANDLES); for (int i = 0; i < lineIndex; i++) OS.pango_layout_iter_next_line(iter); PangoRectangle rect = new PangoRectangle(); OS.pango_layout_iter_get_line_extents(iter, null, rect); OS.pango_layout_iter_free(iter); int x = OS.PANGO_PIXELS(rect.x); int y = OS.PANGO_PIXELS(rect.y); int width = OS.PANGO_PIXELS(rect.width); int height = OS.PANGO_PIXELS(rect.height); if (ascentInPoints != -1 && descentInPoints != -1) { height = Math.max (height, DPIUtil.autoScaleUp(getDevice(), ascentInPoints + descentInPoints)); } x += Math.min (indent, wrapIndent); return new Rectangle(x, y, width, height); } This method repeats the call to OS.pango_layout_get_line_count. Also things like computeRuns() and OS.pango_layout_get_iter(layout) could be done once per TextLayout.getBounds call. Done in a loop this quickly escalates to slow performance. I believe TextLayout.getBounds() should be refactored to minimize repeated calls and reuse results.