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DWrite: Add fallback for OS versions up to Windows 8

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IDWriteGlyphRunAnalysis supports gray-scale antialiasing only when
created via IDWriteFactory2 (and newer), introduced in Windows 8.1

Fallback to using DIrect2D on A8 targets when IDWriteFactory2 is
not available.
This commit is contained in:
Luca Bacci 2025-01-08 10:32:37 +01:00
parent 78fca779ba
commit 4d141f08fb
1 changed files with 83 additions and 0 deletions
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83
src/win32/cairo-dwrite-font.cpp
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@ -1319,6 +1319,81 @@ _cairo_dwrite_scaled_font_init_glyph_color_surface(cairo_dwrite_scaled_font_t *s
return CAIRO_INT_STATUS_SUCCESS;
}
// Helper for OS versions up to Windows 8
static cairo_int_status_t
init_glyph_surface_fallback_a8 (cairo_dwrite_scaled_font_t *scaled_font,
cairo_scaled_glyph_t *scaled_glyph,
int width,
int height,
double x1,
double y1,
DWRITE_MATRIX *matrix,
DWRITE_GLYPH_RUN *run)
{
RefPtr<IWICBitmap> bitmap;
HRESULT hr;
hr = WICImagingFactory::Instance()->CreateBitmap ((UINT)width,
(UINT)height,
GUID_WICPixelFormat8bppAlpha,
WICBitmapCacheOnLoad,
&bitmap);
if (FAILED(hr))
return _cairo_dwrite_error (hr, "CreateBitmap failed");
D2D1_RENDER_TARGET_PROPERTIES properties = D2D1::RenderTargetProperties(
D2D1_RENDER_TARGET_TYPE_DEFAULT,
D2D1::PixelFormat(
DXGI_FORMAT_A8_UNORM,
D2D1_ALPHA_MODE_PREMULTIPLIED),
0,
0,
D2D1_RENDER_TARGET_USAGE_NONE,
D2D1_FEATURE_LEVEL_DEFAULT);
RefPtr<ID2D1RenderTarget> rt;
hr = D2DFactory::Instance()->CreateWicBitmapRenderTarget (bitmap, properties, &rt);
if (FAILED(hr))
return _cairo_dwrite_error (hr, "CreateWicBitmapRenderTarget failed");
RefPtr<ID2D1SolidColorBrush> brush;
hr = rt->CreateSolidColorBrush(D2D1::ColorF(D2D1::ColorF::Black, 1.0), &brush);
rt->BeginDraw();
rt->SetTransform(*(D2D1_MATRIX_3X2_F*)matrix);
rt->DrawGlyphRun({0, 0}, run, brush, scaled_font->measuring_mode);
hr = rt->EndDraw();
if (FAILED(hr))
return _cairo_dwrite_error (hr, "EndDraw failed");
// TODO: rt->Flush()?
cairo_surface_t *surface = cairo_image_surface_create (CAIRO_FORMAT_A8, width, height);
if (cairo_surface_status (surface))
return CAIRO_INT_STATUS_UNSUPPORTED;
// Tell pixman that it should use component alpha blending when the surface is
// used as a source
pixman_image_set_component_alpha (((cairo_image_surface_t*)surface)->pixman_image, TRUE);
int stride = cairo_image_surface_get_stride (surface);
WICRect rect = { 0, 0, width, height };
bitmap->CopyPixels(&rect,
stride,
height * stride,
cairo_image_surface_get_data (surface));
cairo_surface_mark_dirty (surface);
cairo_surface_set_device_offset (surface, -x1, -y1);
_cairo_scaled_glyph_set_surface (scaled_glyph,
&scaled_font->base,
(cairo_image_surface_t*)surface);
return CAIRO_INT_STATUS_SUCCESS;
}
static cairo_int_status_t
_cairo_dwrite_scaled_font_init_glyph_surface (cairo_dwrite_scaled_font_t *scaled_font,
cairo_scaled_glyph_t *scaled_glyph)
@ -1481,6 +1556,14 @@ _cairo_dwrite_scaled_font_init_glyph_surface (cairo_dwrite_scaled_font_t *scaled
&dwrite_glyph_run_analysis);
}
else {
if (antialias == ANTIALIAS_GRAY) {
// IDWriteGlyphRunAnalysis supports gray-scale antialiasing only when
// created from IDWriteFactory2 or later. If we have IDWriteFactory
// only, fallback to rendering with Direct2D on A8 targets.
return init_glyph_surface_fallback_a8 (scaled_font, scaled_glyph,
width, height, x1, y1, &matrix, &run);
}
hr = DWriteFactory::Instance()->CreateGlyphRunAnalysis(&run, 1,
&matrix,
rendering_mode,