Repository navigation
Use the shared color blend helper from SWT #4486
Description
Blending two RGB values by a ratio is implemented over a dozen times in platform.ui, each with its own parameter type and rounding.
Following the discussion in #4489, SWT now provides the shared helper: RGB.blend(RGB other, double weight) and RGBA.blend(RGBA other, double weight) (eclipse-platform/eclipse.platform.swt#3732, @since 3.136).
The weight is the share of other, from 0 (the receiver) to 1 (other), and channels are rounded to the nearest integer.
Work to do in platform.ui, once SWT 3.136 is in the target platform:
- Raise the
org.eclipse.swtlower bound to 3.136 in each touched bundle'sMANIFEST.MF. - Replace the private copies with
RGB.blend:
| Bundle | Copy | Replacement |
|---|---|---|
| jface | PopupDialog.blend(bg, fg, factor) |
bg.blend(fg, factor) |
| jface.databinding | SWTUtil.mix(rgb1, rgb2, ratio) |
rgb2.blend(rgb1, ratio) |
| jface.text | Colors.blend(bg, fg, factor), projection SourceViewerInformationControl.blend |
bg.blend(fg, factor) |
| jface.text | OverviewRuler.interpolate(fg, bg, scale), DiffPainter.interpolate |
fg.blend(bg, scale) |
| ui.editors | SourceViewerInformationControl.blend(bg, fg, factor) |
bg.blend(fg, factor) |
| ui.workbench | ShowViewDialog.blend(c1, c2, ratio) |
c2.blend(c1, ratio / 100.0) |
| ui.workbench | HeapStatus.blend(fg, bg) (40% foreground) |
bg.getRGB().blend(fg.getRGB(), 0.4) |
| e4 renderers | CTabRendering.blend(c1, c2, ratio) |
c2.blend(c1, ratio / 100.0) |
- Keep the public API and let it delegate:
FormColors.blend(c1, c2, ratio)andColorUtil.blend(c1, c2, ratio)becomec2.blend(c1, ratio / 100.0), andColorUtil.blend(val1, val2)becomesval1.blend(val2, 0.5).
The copies truncate while RGB.blend rounds, so a migrated color can differ by one per channel.
Tests that compare exact RGB values need adjusting rather than a rounding shim.
Copies in other repositories (Compare in eclipse.platform, JDT UI, PDE, GEF Classic's FigureUtilities) can follow the same way.
Activity
ptziegler commentedon Oct 13, 2026
Not just the Platform uses such a helper method . Having a "central" blend function would be very much appreciated. I'm not sure if
JFaceColorsis the best place to put it, because it doesn't really fit the description:But I also don't see a better place to put it.
Provide a shared color blend helper in JFaceColors
Provide a shared color blend helper in JFaceColors
laeubi commentedon Oct 14, 2026
See my comment here I think it makes much sense to add this to SWT directly instead especially as your claim
vogella commentedon Oct 14, 2026
See eclipse-platform/eclipse.platform.swt#3732
[-]Provide a shared color blend helper in JFace[/-][+]Use the shared color blend helper from SWT[/+]