From 97b9a80e3c18da5775fe52e43f4502ddbae86ee4 Mon Sep 17 00:00:00 2001 From: Markus Fritsche Date: Tue, 28 Apr 2026 19:49:35 +0000 Subject: [PATCH] upstream-submissions/qt6-base-fourier: bugreports.qt.io draft MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Bug-report body for filing the qt6-base-fourier patch series at bugreports.qt.io against QtBase: OpenGL. Captures: - The summary (GL_ALPHA hard-coded for QT_CONFIG(opengles2), spec-violating in OpenGL ES 3.x). - Reproduction steps (any Mali-class hardware running Plasma Wayland + Qt 6, watch the journal for kwin_wayland's GL debug output). - The four affected sites in qtbase (qopengltextureglyphcache.cpp ×2, qrhigles2.cpp, qopengltextureuploader.cpp). - The fix shape and the runtime predicate added by each patch. - Validation context on ohm (RK3566 PineTab2, mainline 6.19, panfrost mesa 26.0.5). - Gerrit submission boilerplate: account setup, per-patch trailers (Bug:, Pick-to:, Change-Id), reviewer suggestions. The patches themselves stay in arch/qt6-base-fourier/ unchanged — the Change-Id and Bug: trailers will be added at submission time once the bug is filed and bugreports.qt.io issues an issue number. The patches are commit-message-ready to upload via git-review master once those trailers land. --- .../qt6-base-fourier/qt-bug-report.md | 150 ++++++++++++++++++ 1 file changed, 150 insertions(+) create mode 100644 upstream-submissions/qt6-base-fourier/qt-bug-report.md diff --git a/upstream-submissions/qt6-base-fourier/qt-bug-report.md b/upstream-submissions/qt6-base-fourier/qt-bug-report.md new file mode 100644 index 000000000..e4f771dc9 --- /dev/null +++ b/upstream-submissions/qt6-base-fourier/qt-bug-report.md @@ -0,0 +1,150 @@ +# bugreports.qt.io issue draft + +**Project**: QtBase +**Component**: OpenGL +**Affects Version/s**: 6.5, 6.6, 6.7, 6.8, 6.9, 6.10, 6.11, 6.12-dev +**Severity**: Significant — affects every Qt 6 GLES3 client on +Mali-class hardware +**Type**: Bug + +--- + +## Summary + +`QOpenGLTextureGlyphCache`, `QRhiGles2::toGlTextureFormat` +(`RED_OR_ALPHA8` case), and `QOpenGLTextureUploader` (`Format_Alpha8` +and `Format_Grayscale8` cases) all hard-code `GL_ALPHA` (and +`GL_LUMINANCE`) as the `glTexImage2D` `internalFormat` when qtbase +is configured with `QT_CONFIG(opengles2)` (true on every aarch64 +Linux distribution shipping Qt 6). `GL_ALPHA` was deprecated as a +valid `glTexImage2D` `internalFormat` in OpenGL ES 3.0 (ES 3.0 spec, +section 3.8.3, table 3.13 — only sized internal formats remain). + +On Mali-class GPUs (mesa panfrost / panthor) under Wayland, KWin +requests an OpenGL ES 3.2 context. Qt's text-glyph cache upload +path then runs the `#else` branch with `GL_ALPHA`, mesa returns +`GL_INVALID_VALUE`, the texture allocation never succeeds, and +every subsequent `glTexSubImage2D` to that texture errors at +level 0. KWin's `glDebugMessageCallback` fills the journal with: + +``` +kwin_wayland: 0x4: GL_INVALID_VALUE in glTexImage2D(internalFormat=GL_ALPHA) +kwin_wayland: 0x4: GL_INVALID_OPERATION in glTexSubImage2D(invalid texture level 0) × N +``` + +…on every text-glyph cache invalidation, every frame, indefinitely. + +## Reproduce + +- Hardware: any Mali-G31 / G52 / G57 / G610 with mesa panfrost or + panthor on Linux (RK3399 / RK3566 / RK3588 board, Pinebook Pro, + PineTab2, CoolPi 4 etc.). +- Software stack: KDE Plasma 6.x Wayland + Qt 6.x built against + this hardware (any Arch Linux ARM, Debian arm64, Ubuntu arm64 + with Plasma). +- Trigger: open any Qt 6 application that renders text and watch + `journalctl --user -u plasma-kwin_wayland.service` (or + equivalent) for the `glTexImage2D(internalFormat=GL_ALPHA)` + line. Examples that trigger reliably: + - `kate` opening any text file + - `dolphin` listing a directory + - any system tray icon update + - any window decoration title-bar redraw + +## Root cause + +Three sites in qtbase 6.x: + +1. `src/opengl/qopengltextureglyphcache.cpp:111-117` — + `createTextureData()` hard-codes `internalFormat = GL_ALPHA` + in the `QT_CONFIG(opengles2)` branch. +2. `src/opengl/qopengltextureglyphcache.cpp:213-217` — + `load_glyph_image_to_texture()` matching path on glyph reupload. +3. `src/gui/rhi/qrhigles2.cpp:1373-1378` — `QRhiGles2::toGlTextureFormat` + `RED_OR_ALPHA8` case is gated only on `caps.coreProfile`, missing + the ES≥3 disjunct. +4. `src/opengl/qopengltextureuploader.cpp:253-275` — `Format_Alpha8` + and `Format_Grayscale8` short-circuit on `context->isOpenGLES()` + before reaching the existing `TextureSwizzle` fallback. + +## Fix + +Three patches (attached as a series), one per file. Each adds a +runtime predicate (variations on `caps.gles && caps.ctxMajor >= 3` +or `ctx->format().majorVersion() >= 3`) so: + +- desktop GL Core profile → `GL_R8` + `GL_RED` (existing behavior) +- desktop GL Compat profile → `GL_ALPHA` (existing behavior) +- **OpenGL ES 3.x → `GL_R8` + `GL_RED`** (new behavior; spec-clean) +- OpenGL ES 2.x → `GL_ALPHA` (preserved) + +Memory layout, swizzle, and shader behavior identical to the +existing core-profile path. No new dependencies. ~9 net lines +added across three files. + +## Validation + +Tested on PineTab2 (RK3566 / Mali-G52 / mainline kernel 6.19.10 / +panfrost mesa 26.0.5 / KDE Plasma 6.6.4 Wayland / Qt 6.11.0 +patched). Before the patches: constant journal stream of +`GL_INVALID_VALUE` during normal desktop interaction. After the +patches: zero `GL_INVALID_VALUE` in a fresh-session journal, +including under heavy text-rendering load. + +Patch series and end-to-end validation context maintained at +https://github.com/marfrit/fourier under `qt6-base-fourier/`. + +## Patch series + +(Three patches will be uploaded in Gerrit format as a single +series with a common Change-Id thread.) + +1. `[PATCH 1/3] QOpenGLTextureGlyphCache: pick GL_R8 on OpenGL ES 3.x` +2. `[PATCH 2/3] QRhiGles2: use GL_R8 for RED_OR_ALPHA8 on OpenGL ES 3.x` +3. `[PATCH 3/3] QOpenGLTextureUploader: route ES 3.x through TextureSwizzle path` + +--- + +# Gerrit submission notes + +(Per Qt's contribution workflow — https://wiki.qt.io/Qt_Contribution_Guidelines) + +## Account setup (one-time) + +1. Create account at https://account.qt.io +2. Sign Qt's CLA (electronic, takes 5 minutes) +3. Configure SSH key at https://codereview.qt-project.org +4. Install `git-review`: `pacman -S git-review` (Arch) or + `pip install git-review` + +## Per-patch commit-message trailers + +Each patch needs Qt-style trailers below the `Signed-off-by`: + +``` +Bug: QTBUG-XXXXX +Pick-to: 6.10 6.9 6.8 6.7 6.6 6.5 +Change-Id: +``` + +`Bug:` is the issue number from bugreports.qt.io (the issue above, +once filed). `Pick-to:` requests cherry-picks to LTS branches — +this fix should backport cleanly to 6.5 (the oldest currently- +supported Qt 6 LTS). + +`Change-Id:` is auto-generated by `git-review`'s commit-msg hook +on first push. + +## Push to Gerrit + +```sh +cd qtbase +# Apply our 3 patches with `git am`, then: +git review master # pushes branch to refs/for/dev +``` + +## Reviewers to add + +- Eskil Abrahamsen Blomfeldt — primary glyph-cache reviewer +- Laszlo Agocs — RHI reviewer +- Volker Hilsheimer — QtGui maintainer