Add Dark Mode Support for TaskDialog (wxMSW) (PR #26311)
Mohmed abdel-fattah
## Summary
This PR adds full dark mode theming support for the native Windows `TaskDialog` API as used by `wxMessageDialog` and `wxProgressDialog` on Windows. When the application enables dark mode via `wxApp::MSWEnableDarkMode()`, the TaskDialog and its child controls now render consistently with the rest of the application's dark theme instead of appearing with the default light system colours.
Fixes #26240
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## Motivation
Previously, calling `wxApp::MSWEnableDarkMode()` successfully applied dark mode to all native `wxWidgets` controls and top-level windows, but the native `TaskDialog` (used by `wxMessageDialog` and `wxProgressDialog`) was left entirely unstyled. This created an obvious visual inconsistency: the rest of the application appeared dark while every message box and progress dialog retained bright white panels.
---
## Changes
### `src/msw/darkmode.cpp`
This is the core of the implementation. The following were added to the existing `wxMSWDarkMode` namespace:
**Colour palette (`TDDarkCol` namespace)**
A dedicated set of `constexpr COLORREF` constants matching `wxDarkModeSettings::GetColour()` values for the primary panel, secondary panel, footnote area, separator, and all text roles (instruction, content, expando, verification, footnote, radio button).
**Per-dialog state (`TDPageState` struct)**
A `thread_local` map (`tls_tdStates`) stores rendering state per `HWND`, including:
- Open theme handles (`HTHEME`) for `TaskDialog`, `TaskDialogStyle`, and `Button` parts
- GDI brushes for each background zone
- A UIA-backed layout cache (`std::vector<TDLayoutElement>`) with bounding rects and automation IDs for each UI element
- Mouse interaction state (hover/press/tracking) for interactive controls
- Logical state (`isExpanded`, `isChecked`) mirrored from window properties
**UIA layout cache (`TDBuildLayoutCache` / `TDUpdateLayoutCache`)**
UI Automation is used to walk the TaskDialog child tree and build a cache of element bounding rects and automation IDs. This avoids hooking individual child windows for hit testing and allows the paint routine to overdraw text and glyphs without relying on private Win32 control classes.
**Paint routines**
- `TDPaintPixelSwap` — On Windows 10 (no native dark TaskDialog theme), performs a pixel-by-pixel colour substitution on the buffered surface, replacing the light `TaskDialog` panel colours with the dark palette
Mohmed abdel-fattah
memoarfaa left a comment (wxWidgets/wxWidgets#26311)Hi @vadz
Could you advise me on whether adding files to darkmode.cpp and darkmode.h is better, or creating separate files for dark mode taskdialog ?
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Mohmed abdel-fattah
@memoarfaa pushed 1 commit.
- 7b45662 Fix build errors
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Mohmed abdel-fattah
@memoarfaa pushed 1 commit.
- f04efe7 Fix Whitespace Errors
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Mohmed abdel-fattah
@memoarfaa pushed 1 commit.
- 68e0139 add luiautomationcore to makfile.gcc
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VZ
Thanks a lot for all this work, it's pretty impressive — and the idea of using UI Automation for this is great.
This mostly looks fine to me, although I admit I didn't look into all the details, the only thing which definitely needs to be done is to replace ATL classes with wx ones, but hopefully it shouldn't be very difficult.
One other annoying thing is that it would be nice to avoid having to link with `uiautomation.lib`, as this breaks any existing makefiles for the applications using static wx libs with MinGW (for MSVC we could use `#pragma comment(lib)`...). What exactly do we need from it? If it's just the UUID, I'd simply hardcode it instead.
Concerning the question of whether it should all go to this file: I think it would be better to create a separate `darktaskdialog.cpp` or something like this.
> @@ -11,6 +11,7 @@
#define _WX_MSW_PRIVATE_DARKMODE_H_
#include "wx/settings.h"
+#include <commctrl.h>
Minor, but we usually do
```suggestion
#include "wx/msw/wrapcctl.h"
```
> @@ -32,6 +32,7 @@
#include "wx/msw/private/msgdlg.h"
#include "wx/evtloop.h"
+#include <wx/msw/private/darkmode.h>
Even more minor, but:
```suggestion
#include "wx/msw/private/darkmode.h"
```
> + // (The old code used TDN_DIALOG_CONSTRUCTED which fires too early
+ // for UI Automation to walk the child windows reliably.)
This was copy-pasted from `wxMessageDialog` but doesn't make sense here, this code never used `TDN_DIALOG_CONSTRUCTED`, so let's just remove it:
```suggestion
```
> +
+ case TDN_EXPANDO_BUTTON_CLICKED:
+ // Store the expanded state as a window property so the subclassed
+ // TaskPage panel can read it during WM_PAINT without a UIA call
Mohmed abdel-fattah
@memoarfaa pushed 1 commit.
- 4d057ed Fix wx style, use wxCOMPtr and wxBasicString and avoid having to link with uiautomation.lib.
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Mohmed abdel-fattah
@memoarfaa pushed 1 commit.
- 6a4ac47 Fix build errors
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Mohmed abdel-fattah
@memoarfaa pushed 1 commit.
- 29190b8 fix error use of C++11 keywords nullptr
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Mohmed abdel-fattah
@memoarfaa pushed 1 commit.
- 48252ab aad wrapwin header try to fix error: ‘TASKDIALOGCONFIG’ does not name a type .
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Mohmed abdel-fattah
@memoarfaa commented on this pull request.
> @@ -44,6 +44,13 @@ #include "wx/msw/private/darkmode.h" +#include <uiautomation.h> +#include <vssym32.h> +#include <commctrl.h> +#include <atlbase.h> // CComPtr, CComBSTR
If use wxCOMPtr and wxBasicString look good now?
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Mohmed abdel-fattah
> + case TDLG_EXPANDOTEXT: return TDDarkCol::kTextExpando;
+ case TDLG_VERIFICATIONTEXT: return TDDarkCol::kTextVerify;
+ case TDLG_FOOTNOTEPANE: return TDDarkCol::kTextFootnote;
+ case TDLG_EXPANDEDFOOTERAREA: return TDDarkCol::kTextFtrExp;
+ case TDLG_RADIOBUTTONPANE: return TDDarkCol::kTextRadio;
+ default: return TDDarkCol::kTextNormal;
+ }
+}
+
+// ============================================================================
+// Icon loading
+// ============================================================================
+
+static HICON TDLoadStockIcon(const TASKDIALOGCONFIG* cfg, bool isMain)
+{
+ if (!cfg) return nullptr;
If style look good now.
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Mohmed abdel-fattah
> #include <memory> #if wxUSE_LOG_TRACE static const char* TRACE_DARKMODE = "msw-darkmode"; #endif // wxUSE_LOG_TRACE +#include <atlwin.h>
removed
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Mohmed abdel-fattah
@memoarfaa commented on this pull request.
> + // (The old code used TDN_DIALOG_CONSTRUCTED which fires too early + // for UI Automation to walk the child windows reliably.)
This not copy-pasted from wxMessageDialog from wxMessageDialog.
it's my old comment for don't use AllowForTaskDialog at TDN_DIALOG_CONSTRUCTED it's need TDN_CREATE
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Mohmed abdel-fattah
@memoarfaa pushed 1 commit.
- 4ca4292 Add wrapcctl header
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VZ
@vadz commented on this pull request.
Thanks for the updates, but there are still some build problems. They look easy to fix (WINAPI missing in one place, just fix formatting — or, preferably, switch to using wxUxThemeHandle — in another) and I'll try to review this once again and merge as soon as this is done. Or I could just fix them myself if you prefer, please let me know.
> + ct == UIA_ScrollBarControlTypeId || ct == UIA_PaneControlTypeId)
+ {
+ HWND hBtn = nullptr;
+ pChild->get_CurrentNativeWindowHandle(reinterpret_cast<UIA_HWND*>(&hBtn));
+ if (hBtn)
+ {
+ BSTR bId; pChild->get_CurrentAutomationId(&bId);
+ const std::wstring id(bId ? static_cast<LPCWSTR>(bId) : L"");
+ HWND hP = GetParent(hBtn);
+
+ if (ct == UIA_ProgressBarControlTypeId)
+ {
+ HTHEME hCE = OpenThemeData(nullptr, L"DarkMode_CopyEngine::Progress");
+ HTHEME hBase = OpenThemeData(nullptr, L"Progress");
+ bool hasCE = (hCE && hCE != hBase);
+ if (hCE) CloseThemeData(hCE); if (hBase) CloseThemeData(hBase);
This statement provokes gcc error in one of the CI builds. As mentioned before, this could be avoided entirely by using wxUxThemeHandle instead of manual open/close theme data calls.
> @@ -24,6 +24,7 @@ // for compilers that support precompilation, includes "wx.h". #include "wx/wxprec.h" +#include "wx/module.h"
Was this moved intentionally? Not really a problem, of course, but just looks weird.
> +
+ EndBufferedPaint(hbp, TRUE);
+}
+
+// ============================================================================
+// Subclass procedures
+// ============================================================================
+
+static LRESULT CALLBACK TDPageSubclassProc(
+ HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam,
+ UINT_PTR uId, DWORD_PTR)
+{
+ switch (msg)
+ {
+ case WM_ERASEBKGND:
+ return 1;
Minor, but this should be
⬇️ Suggested change- return 1; + return TRUE;
> + FillRect(hdc, &rc, reinterpret_cast<HBRUSH>(dwRef)); return 1;
+ }
+ break;
+ case WM_CTLCOLORMSGBOX:
+ case WM_CTLCOLOREDIT:
+ case WM_CTLCOLORLISTBOX:
+ case WM_CTLCOLORBTN:
+ case WM_CTLCOLORDLG:
+ case WM_CTLCOLORSCROLLBAR:
+ case WM_CTLCOLORSTATIC:
+ {
+ HDC hdc = reinterpret_cast<HDC>(wParam);
+ COLORREF bg = TDDarkCol::kSecondary;
+ if (dwRef) { LOGBRUSH lb = {}; GetObject(reinterpret_cast<HBRUSH>(dwRef), sizeof(lb), &lb); if (lb.lbStyle == BS_SOLID) bg = lb.lbColor; }
+ SetBkColor(hdc, bg); SetTextColor(hdc, TDDarkCol::kTextNormal);
+ return reinterpret_cast<LRESULT>(dwRef ? reinterpret_cast<HBRUSH>(dwRef) : CreateSolidBrush(TDDarkCol::kSecondary));
Isn't this brush leaked?
> + // Mouse interaction (message-driven, no polling)
+ bool tracking = false;
+ bool pressing = false;
+ int hotIdx = -1;
+
+ // Logical dialog state
+ bool isExpanded = false;
+ bool isChecked = false;
+ bool defExpanded = false;
+ bool defChecked = false;
+
+ const TASKDIALOGCONFIG* pCfg = nullptr;
+
+ void CloseThemes()
+ {
+ if (hTD) { CloseThemeData(hTD); hTD = nullptr; }
It would be really nice to avoid putting more than one statement per line, this improves readability a lot, in general, e.g.
⬇️ Suggested change- if (hTD) { CloseThemeData(hTD); hTD = nullptr; }
+ if (hTD)
+ {
+ CloseThemeData(hTD);
+ hTD = nullptr;
+ }
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Mohmed abdel-fattah
@memoarfaa pushed 1 commit.
- 459d4ee Add wxUxThemeHandle instead of HTHEME
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Mohmed abdel-fattah
@memoarfaa pushed 1 commit.
- b9d5717 Add static Enumes Fix lambda 32-bit MinGW builds WNDENUMPROC
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Mohmed abdel-fattah
@memoarfaa pushed 1 commit.
- 33b871d add GetWindowDPI
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VZ
vadz left a comment (wxWidgets/wxWidgets#26311)Just wanted to check: do you plan to make more changes here or should I merge this (I'll make some changes myself if I do it)?
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Maarten
MaartenBent left a comment (wxWidgets/wxWidgets#26311)I (finally) tried this, and it looks great. One of Vadz remarks is about leaking a brush, and this (or other leaks) are indeed happening. After showing the about dialog in the minimal sample and closing the app, Visual Studio reports multiple memory leaks.
On both Windows 10 and 11 the progress dialog has a white bar. The screenshot in the reference implementation has a dark bar. When I run the reference implementation (on Windows 10) it is also white. Is this a bug?
Screenshot.2026-06-01.233203.png (view on web)—
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VZ
vadz left a comment (wxWidgets/wxWidgets#26311)After showing the about dialog in the minimal sample and closing the app, Visual Studio reports multiple memory leaks.
FWIW I do plan to fix this and merge this PR soon, i.e. before 3.3.3.
On both Windows 10 and 11 the progress dialog has a white bar.
I think this is indeed a bug, but it's still worth merging even without fixing it.
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Maarten
MaartenBent left a comment (wxWidgets/wxWidgets#26311)I was using a Windows 11 24h2, it might only work in newer Windows 11 that has DarkMode_DarkTheme or better DarkMode_CopyEngine themes. I'll try that later.
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