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[conhost] Fix WM_GETDPISCALEDSIZE handler, use provided size instead of current window size #18268

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[conhost] Fix WM_GETDPISCALEDSIZE handler, use provided size instead of current window size #18268

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88e8d24
rewrite conhost WM_GETDPISCALEDSIZE handler
Dec 1, 2024
f6093ec
comments, format script
Dec 20, 2024
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1 change: 1 addition & 0 deletions src/cascadia/ut_app/TerminalApp.Unit.Tests.manifest
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@
UI Variable, GH #12452 -->
<maxversiontested Id="10.0.22000.0"/>
<maxversiontested Id="10.0.22621.0"/>
<maxversiontested Id="10.0.26100.0"/>
<supportedOS Id="{8e0f7a12-bfb3-4fe8-b9a5-48fd50a15a9a}" />
</application>
</compatibility>
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24 changes: 24 additions & 0 deletions src/interactivity/win32/window.cpp
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Expand Up @@ -964,6 +964,30 @@ void Window::s_CalculateWindowRect(const til::size coordWindowInChars,
prectWindow->bottom = prectWindow->top + rectProposed.height();
}

// Expands a rect by the size of the non-client area (caption bar, resize borders,
// scroll bars, etc), which depends on the window styles and DPI
void Window::s_ExpandRectByNonClientSize(HWND const hWnd,
UINT dpi,
_Inout_ til::rect* const prectWindow)
{
DWORD dwStyle = GetWindowStyle(hWnd);
DWORD dwExStyle = GetWindowExStyle(hWnd);
BOOL fMenu = FALSE;

ServiceLocator::LocateWindowMetrics<WindowMetrics>()->AdjustWindowRectEx(
prectWindow, dwStyle, fMenu, dwExStyle, dpi);

// Note: AdjustWindowRectEx does not account for scroll bars :(.
if (WI_IsFlagSet(dwStyle, WS_HSCROLL))
{
prectWindow->bottom += ServiceLocator::LocateHighDpiApi<WindowDpiApi>()->GetSystemMetricsForDpi(SM_CYHSCROLL, dpi);
}
if (WI_IsFlagSet(dwStyle, WS_VSCROLL))
{
prectWindow->bottom += ServiceLocator::LocateHighDpiApi<WindowDpiApi>()->GetSystemMetricsForDpi(SM_CXVSCROLL, dpi);
}
}

til::rect Window::GetWindowRect() const noexcept
{
RECT rc{};
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4 changes: 4 additions & 0 deletions src/interactivity/win32/window.hpp
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Expand Up @@ -135,6 +135,7 @@ namespace Microsoft::Console::Interactivity::Win32
void _HandleDrop(const WPARAM wParam) const;
[[nodiscard]] HRESULT _HandlePaint() const;
void _HandleWindowPosChanged(const LPARAM lParam);
bool _HandleGetDpiScaledSize(UINT dpiNew, _Inout_ SIZE* pSizeNew) const;

// Accessibility/UI Automation
[[nodiscard]] LRESULT _HandleGetObject(const HWND hwnd,
Expand Down Expand Up @@ -173,6 +174,9 @@ namespace Microsoft::Console::Interactivity::Win32
const til::size coordBufferSize,
_In_opt_ HWND const hWnd,
_Inout_ til::rect* const prectWindow);
static void s_ExpandRectByNonClientSize(HWND const hWnd,
UINT dpi,
_Inout_ til::rect* const prectWindow);

static void s_ReinitializeFontsForDPIChange();

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97 changes: 60 additions & 37 deletions src/interactivity/win32/windowproc.cpp
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Expand Up @@ -244,43 +244,12 @@ static constexpr TsfDataProvider s_tsfDataProvider;

case WM_GETDPISCALEDSIZE:
{
// This message will send us the DPI we're about to be changed to.
// Our goal is to use it to try to figure out the Window Rect that we'll need at that DPI to maintain
// the same client rendering that we have now.

// First retrieve the new DPI and the current DPI.
const auto dpiProposed = (WORD)wParam;

// Now we need to get what the font size *would be* if we had this new DPI. We need to ask the renderer about that.
const auto& fiCurrent = ScreenInfo.GetCurrentFont();
FontInfoDesired fiDesired(fiCurrent);
FontInfo fiProposed(L"", 0, 0, { 0, 0 }, 0);

const auto hr = g.pRender->GetProposedFont(dpiProposed, fiDesired, fiProposed);
// fiProposal will be updated by the renderer for this new font.
// GetProposedFont can fail if there's no render engine yet.
// This can happen if we're headless.
// Just assume that the font is 1x1 in that case.
const auto coordFontProposed = SUCCEEDED(hr) ? fiProposed.GetSize() : til::size{ 1, 1 };

// Then from that font size, we need to calculate the client area.
// Then from the client area we need to calculate the window area (using the proposed DPI scalar here as well.)

// Retrieve the additional parameters we need for the math call based on the current window & buffer properties.
const auto viewport = ScreenInfo.GetViewport();
auto coordWindowInChars = viewport.Dimensions();

const auto coordBufferSize = ScreenInfo.GetTextBuffer().GetSize().Dimensions();

// Now call the math calculation for our proposed size.
til::rect rectProposed;
s_CalculateWindowRect(coordWindowInChars, dpiProposed, coordFontProposed, coordBufferSize, hWnd, &rectProposed);

// Prepare where we're going to keep our final suggestion.
const auto pSuggestionSize = (SIZE*)lParam;

pSuggestionSize->cx = rectProposed.width();
pSuggestionSize->cy = rectProposed.height();
SIZE* pSizeNew = (SIZE*)lParam;
UINT dpiNew = (WORD)wParam;
if (!_HandleGetDpiScaledSize(dpiNew, pSizeNew))
{
return FALSE;
}

// Format our final suggestion for consumption.
UnlockConsole();
Expand Down Expand Up @@ -884,6 +853,60 @@ void Window::_HandleWindowPosChanged(const LPARAM lParam)
}
}

// WM_GETDPISCALEDSIZE is sent prior to the window changing DPI, allowing us to
// choose the size at the new DPI (overriding the default, linearly scaled).
//
// This is used to keep the rows and columns from changing when the DPI changes.
bool Window::_HandleGetDpiScaledSize(UINT dpiNew, _Inout_ SIZE* pSizeNew) const
{
// Get the current DPI and font size.
HWND hwnd = GetWindowHandle();
UINT dpiCurrent = ServiceLocator::LocateHighDpiApi<WindowDpiApi>()->GetDpiForWindow(hwnd);
const auto& fontInfoCurrent = GetScreenInfo().GetCurrentFont();
til::size fontSizeCurrent = fontInfoCurrent.GetSize();

// Scale the current font to the new DPI and get the new font size.
FontInfoDesired fontInfoDesired(fontInfoCurrent);
FontInfo fontInfoNew(L"", 0, 0, { 0, 0 }, 0);
if (!SUCCEEDED(ServiceLocator::LocateGlobals().pRender->GetProposedFont(
dpiNew, fontInfoDesired, fontInfoNew)))
{
return false;
}
Comment on lines +871 to +875
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Is there a reason you chose to replace the previous

const auto coordFontProposed = SUCCEEDED(hr) ? fiProposed.GetSize() : til::size{ 1, 1 };

?

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Is the question about handling cases where getting the speculative font fails? If we cannot resolve the new font size, the new version will return false from WM_GETDPISCALEDSIZE, instead of filling in a size. This falls back to default processing, window size linearly scaled for dpi change.

til::size fontSizeNew = fontInfoNew.GetSize();

// The provided size is the window rect, which includes non-client area
// (caption bars, resize borders, scroll bars, etc). We want to scale the
// client area separately from the non-client area. The client area will be
// scaled using the new/old font sizes, so that the size of the grid (rows/
// columns) does not change.

// Subtract the size of the window's current non-client area from the
// provided size. This gives us the new client area size at the previous DPI.
til::rect rc;
s_ExpandRectByNonClientSize(hwnd, dpiCurrent, &rc);
pSizeNew->cx -= rc.width();
pSizeNew->cy -= rc.height();

// Scale the size of the client rect by the new/old font sizes.
pSizeNew->cx = MulDiv(pSizeNew->cx, fontSizeNew.width, fontSizeCurrent.width);
pSizeNew->cy = MulDiv(pSizeNew->cy, fontSizeNew.height, fontSizeCurrent.height);

// Add the size of the non-client area at the new DPI to the final size,
// getting the new window rect (the output of this function).
rc = { 0, 0, pSizeNew->cx, pSizeNew->cy };
s_ExpandRectByNonClientSize(hwnd, dpiNew, &rc);

// Write the final size to the out parameter.
// If not Maximized/Arranged (snapped), this will determine the size of the
// rect in the WM_DPICHANGED message. Otherwise, the provided size is the
// normal position (restored, last non-Maximized/Arranged).
pSizeNew->cx = rc.width();
pSizeNew->cy = rc.height();

return true;
}

// Routine Description:
// - This helper method for the window procedure will handle the WM_PAINT message
// - It will retrieve the invalid rectangle and dispatch that information to the attached renderer
Expand Down
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