Add wxUxThemeHandle::GetTrueSize() and GetDrawSize() helpers

These functions are more convenient to use and, arguably, more clear to
read than calls to ::GetThemePartSize(), so add these wrappers and
replace most of the uses of the Win32 function with them.

This shouldn't result in any real changes to behaviour.

include/wx/msw/uxtheme.h

@@ -218,6 +218,21 @@ public:
     // GetThemeColor() because we want to default the state.
     wxColour GetColour(int part, int prop, int state = 0) const;
 
+    // Return the size of a theme element, either "as is" (TS_TRUE size) or as
+    // it would be used for drawing (TS_DRAW size).
+    //
+    // For now we don't allow specifying the HDC or rectangle as they don't
+    // seem to be useful.
+    wxSize GetTrueSize(int part, int state = 0) const
+    {
+        return DoGetSize(part, state, TS_TRUE);
+    }
+
+    wxSize GetDrawSize(int part, int state = 0) const
+    {
+        return DoGetSize(part, state, TS_DRAW);
+    }
+
     // Draw theme background: if the caller already has a RECT, it can be
     // provided directly, otherwise wxRect is converted to it.
     void DrawBackground(HDC hdc, const RECT& rc, int part, int state = 0);
@@ -233,6 +248,9 @@ private:
     {
     }
 
+    wxSize DoGetSize(int part, int state, THEMESIZE ts) const;
+
+
     // This is almost, but not quite, const: it's only reset in move ctor.
     HTHEME m_hTheme;
 

src/aui/barartmsw.cpp

@@ -35,31 +35,19 @@ wxAuiMSWToolBarArt::wxAuiMSWToolBarArt()
         wxWindow* window = static_cast<wxApp*>(wxApp::GetInstance())->GetTopWindow();
         wxUxThemeHandle hTheme(window, L"Rebar");
 
-        SIZE overflowSize;
-        ::GetThemePartSize(hTheme, nullptr, RP_CHEVRON, 0,
-            nullptr, TS_TRUE, &overflowSize);
-        m_overflowSize = overflowSize.cx;
+        m_overflowSize = hTheme.GetTrueSize(RP_CHEVRON).x;
 
-        SIZE gripperSize;
-        ::GetThemePartSize(hTheme, nullptr, RP_GRIPPER, 0,
-            nullptr, TS_TRUE, &gripperSize);
-        m_gripperSize = gripperSize.cx;
+        m_gripperSize = hTheme.GetTrueSize(RP_GRIPPER).x;
 
         wxUxThemeHandle hThemeToolbar(window, L"Toolbar");
 
-        SIZE seperatorSize;
-        ::GetThemePartSize(hThemeToolbar, nullptr, TP_SEPARATOR, 0,
-            nullptr, TS_TRUE, &seperatorSize);
-        m_separatorSize = seperatorSize.cx;
+        m_separatorSize = hThemeToolbar.GetTrueSize(TP_SEPARATOR).x;
 
         // TP_DROPDOWNBUTTON is only 7px, too small to fit the dropdown arrow,
         // use 14px instead.
         m_dropdownSize = window->FromDIP(14);
 
-        SIZE buttonSize;
-        ::GetThemePartSize(hThemeToolbar, nullptr, TP_BUTTON, 0,
-            nullptr, TS_TRUE, &buttonSize);
-        m_buttonSize.Set(buttonSize.cx, buttonSize.cy);
+        m_buttonSize = hThemeToolbar.GetTrueSize(TP_BUTTON);
     }
     else
         m_themed = false;

src/aui/tabartmsw.cpp

@@ -428,21 +428,14 @@ int wxAuiMSWTabArt::GetBestTabCtrlSize(wxWindow* wnd,
     return wxAuiGenericTabArt::GetBestTabCtrlSize(wnd, pages, requiredBmp_size);
 }
 
-void wxAuiMSWTabArt::InitSizes(wxWindow* wnd, wxDC& dc)
+void wxAuiMSWTabArt::InitSizes(wxWindow* wnd, wxDC& WXUNUSED(dc))
 {
-    SIZE uxSize;
-
     // Borrow close button from tooltip (best fit on various backgrounds)
     wxUxThemeHandle hTooltipTheme(wnd, L"Tooltip");
-
-    ::GetThemePartSize(hTooltipTheme, GetHdcOf(dc.GetTempHDC()),
-        TTP_CLOSE, 0, nullptr, TS_TRUE, &uxSize);
-    m_closeBtnSize.Set(uxSize.cx, uxSize.cy);
+    m_closeBtnSize = hTooltipTheme.GetTrueSize(TTP_CLOSE);
 
     wxUxThemeHandle hTabTheme(wnd, L"Tab");
-    ::GetThemePartSize(hTabTheme, GetHdcOf(dc.GetTempHDC()),
-        TABP_TABITEM, 0, nullptr, TS_TRUE, &uxSize);
-    m_tabSize.Set(uxSize.cx, uxSize.cy);
+    m_tabSize = hTabTheme.GetTrueSize(TABP_TABITEM);
 }
 
 bool wxAuiMSWTabArt::IsThemed() const

src/msw/renderer.cpp

@@ -846,9 +846,7 @@ wxSize wxRendererXP::GetCheckBoxSize(wxWindow* win, int flags)
     {
         if (::IsThemePartDefined(hTheme, BP_CHECKBOX, 0))
         {
-            SIZE checkSize;
-            if (::GetThemePartSize(hTheme, nullptr, BP_CHECKBOX, CBS_UNCHECKEDNORMAL, nullptr, TS_DRAW, &checkSize) == S_OK)
-                return wxSize(checkSize.cx, checkSize.cy);
+            return hTheme.GetDrawSize(BP_CHECKBOX, CBS_UNCHECKEDNORMAL);
         }
     }
     return m_rendererNative.GetCheckBoxSize(win, flags);
@@ -863,9 +861,7 @@ wxSize wxRendererXP::GetCheckMarkSize(wxWindow* win)
     {
         if (::IsThemePartDefined(hTheme, MENU_POPUPCHECK, 0))
         {
-            SIZE checkSize;
-            if (::GetThemePartSize(hTheme, nullptr, MENU_POPUPCHECK, MC_CHECKMARKNORMAL, nullptr, TS_DRAW, &checkSize) == S_OK)
-                return wxSize(checkSize.cx, checkSize.cy);
+            return hTheme.GetDrawSize(MENU_POPUPCHECK, MC_CHECKMARKNORMAL);
         }
     }
     return m_rendererNative.GetCheckMarkSize(win);
@@ -880,11 +876,7 @@ wxSize wxRendererXP::GetExpanderSize(wxWindow* win)
     {
         if ( ::IsThemePartDefined(hTheme, TVP_GLYPH, 0) )
         {
-            SIZE expSize;
-            if (::GetThemePartSize(hTheme, nullptr, TVP_GLYPH, GLPS_CLOSED, nullptr,
-                                   TS_DRAW, &expSize) == S_OK)
-                return wxSize(expSize.cx, expSize.cy);
-
+            return hTheme.GetDrawSize(TVP_GLYPH, GLPS_CLOSED);
         }
     }
 
@@ -968,19 +960,10 @@ wxSize wxRendererXP::GetCollapseButtonSize(wxWindow *win, wxDC& dc)
 
     if ( ::IsThemePartDefined(hTheme, TDLG_EXPANDOBUTTON, 0) )
     {
-        SIZE s;
-        ::GetThemePartSize(hTheme,
-            GetHdcOf(dc.GetTempHDC()),
-            TDLG_EXPANDOBUTTON,
-            TDLGEBS_NORMAL,
-            nullptr,
-            TS_TRUE,
-            &s);
-
-        return wxSize(s.cx, s.cy);
+        return hTheme.GetTrueSize(TDLG_EXPANDOBUTTON, TDLGEBS_NORMAL);
     }
-    else
-        return m_rendererNative.GetCollapseButtonSize(win, dc);
+
+    return m_rendererNative.GetCollapseButtonSize(win, dc);
 }
 
 void

src/msw/uxtheme.cpp

@@ -83,6 +83,23 @@ wxColour wxUxThemeHandle::GetColour(int part, int prop, int state) const
     return wxRGBToColour(col);
 }
 
+wxSize wxUxThemeHandle::DoGetSize(int part, int state, THEMESIZE ts) const
+{
+    SIZE size;
+    HRESULT hr = ::GetThemePartSize(m_hTheme, nullptr, part, state, nullptr, ts,
+                                    &size);
+    if ( FAILED(hr) )
+    {
+        wxLogApiError(
+            wxString::Format("GetThemePartSize(%i, %i)", part, state),
+            hr
+        );
+        return {};
+    }
+
+    return wxSize{size.cx, size.cy};
+}
+
 void
 wxUxThemeHandle::DrawBackground(HDC hdc, const RECT& rc, int part, int state)
 {