Merge branch 'dark-mode-collapse-button'

Improve collapse button appearance in dark mode.

See #23098.

include/wx/msw/private/darkmode.h

@@ -39,7 +39,12 @@ wxColour GetColour(wxSystemColour index);
 // Return the background brush to be used by default in dark mode.
 HBRUSH GetBackgroundBrush();
 
-// If dark mode is active, paint the given window using inverted colours.
+// Invert the colours of the given bitmap trying to keep it readable.
+wxBitmap InvertBitmap(const wxBitmap& bmp);
+
+// If dark mode is active, paint the given window using inverted colours by
+// drawing it normally and then applying InvertBitmap() to it.
+//
 // Otherwise just return false without doing anything.
 //
 // This can only be called from WM_PAINT handler for a native control and

src/msw/darkmode.cpp

@@ -353,6 +353,35 @@ HBRUSH GetBackgroundBrush()
     return brush ? GetHbrushOf(*brush) : 0;
 }
 
+wxBitmap InvertBitmap(const wxBitmap& bmp)
+{
+#if wxUSE_IMAGE
+    wxImage image = bmp.ConvertToImage();
+
+    unsigned char *data = image.GetData();
+    const int len = image.GetWidth()*image.GetHeight();
+    for ( int i = 0; i < len; ++i, data += 3 )
+    {
+        wxImage::RGBValue rgb(data[0], data[1], data[2]);
+        wxImage::HSVValue hsv = wxImage::RGBtoHSV(rgb);
+
+        // There is no really good way to convert normal colours to dark mode,
+        // but try to do a bit better than just inverting the value because
+        // this results in colours which are much too dark.
+        hsv.value = sqrt(1.0 - hsv.value*hsv.value);
+
+        rgb = wxImage::HSVtoRGB(hsv);
+        data[0] = rgb.red;
+        data[1] = rgb.green;
+        data[2] = rgb.blue;
+    }
+
+    return wxBitmap(image);
+#else // !wxUSE_IMAGE
+    return wxBitmap();
+#endif // wxUSE_IMAGE/!wxUSE_IMAGE
+}
+
 bool PaintIfNecessary(HWND hwnd, WXWNDPROC defWndProc)
 {
 #if wxUSE_IMAGE
@@ -378,28 +407,9 @@ bool PaintIfNecessary(HWND hwnd, WXWNDPROC defWndProc)
             ::DefWindowProc(hwnd, WM_PAINT, wparam, 0);
     }
 
-    wxImage image = bmp.ConvertToImage();
-
-    unsigned char *data = image.GetData();
-    for ( int i = 0; i < size.x*size.y; ++i, data += 3 )
-    {
-        wxImage::RGBValue rgb(data[0], data[1], data[2]);
-        wxImage::HSVValue hsv = wxImage::RGBtoHSV(rgb);
-
-        // There is no really good way to convert normal colours to dark mode,
-        // but try to do a bit better than just inverting the value because
-        // this results in colours which are much too dark.
-        hsv.value = sqrt(1.0 - hsv.value*hsv.value);
-
-        rgb = wxImage::HSVtoRGB(hsv);
-        data[0] = rgb.red;
-        data[1] = rgb.green;
-        data[2] = rgb.blue;
-    }
-
     PAINTSTRUCT ps;
     wxDCTemp dc(::BeginPaint(hwnd, &ps), size);
-    dc.DrawBitmap(wxBitmap(image), 0, 0);
+    dc.DrawBitmap(InvertBitmap(bmp), 0, 0);
     ::EndPaint(hwnd, &ps);
 
     return true;
@@ -649,6 +659,11 @@ HBRUSH GetBackgroundBrush()
     return 0;
 }
 
+wxBitmap InvertBitmap(const wxBitmap& WXUNUSED(bmp))
+{
+    return wxBitmap();
+}
+
 bool PaintIfNecessary(HWND WXUNUSED(hwnd), WXWNDPROC WXUNUSED(defWndProc))
 {
     return false;

src/msw/renderer.cpp

@@ -25,6 +25,7 @@
     #include "wx/window.h"
     #include "wx/control.h"     // for wxControl::Ellipsize()
     #include "wx/dc.h"
+    #include "wx/dcmemory.h"
     #include "wx/settings.h"
 #endif //WX_PRECOMP
 
@@ -38,6 +39,8 @@
 #include "wx/msw/wrapcctl.h"
 #include "wx/dynlib.h"
 
+#include "wx/msw/private/darkmode.h"
+
 // ----------------------------------------------------------------------------
 // methods common to wxRendererMSW and wxRendererXP
 // ----------------------------------------------------------------------------
@@ -927,11 +930,8 @@ wxSize wxRendererXP::GetExpanderSize(wxWindow* win)
     return m_rendererNative.GetExpanderSize(win);
 }
 
-void
-wxRendererXP::DrawCollapseButton(wxWindow *win,
-                                 wxDC& dc,
-                                 const wxRect& rect,
-                                 int flags)
+static bool
+DoDrawCollapseButton(wxWindow* win, HDC hdc, RECT r, int flags)
 {
     wxUxThemeHandle hTheme(win, L"TASKDIALOG");
 
@@ -948,20 +948,62 @@ wxRendererXP::DrawCollapseButton(wxWindow *win,
         if ( flags & wxCONTROL_EXPANDED )
             state += 3;
 
-        RECT r = ConvertToRECT(dc, rect);
-
         ::DrawThemeBackground
             (
             hTheme,
-            GetHdcOf(dc.GetTempHDC()),
+            hdc,
             TDLG_EXPANDOBUTTON,
             state,
             &r,
             nullptr
             );
+        return true;
+    }
+
+    return false;
+}
+
+void
+wxRendererXP::DrawCollapseButton(wxWindow *win,
+                                 wxDC& dc,
+                                 const wxRect& rect,
+                                 int flags)
+{
+    RECT r = ConvertToRECT(dc, rect);
+
+    // Default theme draws the button on light background which looks very out
+    // of place when using dark mode, so invert it if necessary and fall back
+    // on the generic version if this fails.
+    //
+    // Ideal would be to find the theme drawing the version appropriate for the
+    // dark mode, but it's unknown if there is one providing this.
+    if ( wxMSWDarkMode::IsActive() )
+    {
+        wxBitmap bmp(rect.GetSize());
+
+        bool ok;
+        {
+            wxMemoryDC mdc(bmp);
+            ok = DoDrawCollapseButton(win, GetHdcOf(mdc), r, flags);
+        }
+
+        if ( ok )
+        {
+            wxBitmap bmpInv = wxMSWDarkMode::InvertBitmap(bmp);
+            if ( bmpInv.IsOk() )
+            {
+                dc.DrawBitmap(bmpInv, rect.GetPosition());
+                return;
+            }
+        }
     }
     else
-        m_rendererNative.DrawCollapseButton(win, dc, rect, flags);
+    {
+        if ( DoDrawCollapseButton(win, GetHdcOf(dc.GetTempHDC()), r, flags) )
+            return;
+    }
+
+    m_rendererNative.DrawCollapseButton(win, dc, rect, flags);
 }
 
 wxSize wxRendererXP::GetCollapseButtonSize(wxWindow *win, wxDC& dc)