Implement aliased text rendering with DirectWrite

This creates aliased glyphs using the DirectWrite engine when
requested.

Note: There was previously a fallback to GDI to support aliased
text, which ignored the hinting settings. This patch also removes
that fallback.

[ChangeLog][Windows] Support QFont::NoAntialias with the DirectWrite
font engine.

Fixes: QTBUG-97645
Change-Id: I587f56ace468cfdd57debe7bc8492a96587a4e05
Reviewed-by: Allan Sandfeld Jensen <[email protected]>
(cherry picked from commit 421e7621faa50bf9007076d6be4e0da9514edc59)
(cherry picked from commit b62b6094dd56c53f6508feaa61b43b49247d25ff)
Reviewed-by: Qt Cherry-pick Bot <[email protected]>

2 files changed, 42 insertions, 11 deletions

diff --git a/src/gui/text/windows/qwindowsfontenginedirectwrite.cpp b/src/gui/text/windows/qwindowsfontenginedirectwrite.cpp
index daa24835696..0233c402ddc 100644
--- a/src/gui/text/windows/qwindowsfontenginedirectwrite.cpp
+++ b/src/gui/text/windows/qwindowsfontenginedirectwrite.cpp
@@ -158,8 +158,11 @@ static DWRITE_MEASURING_MODE renderModeToMeasureMode(DWRITE_RENDERING_MODE rende
     }
 }
 
-static DWRITE_RENDERING_MODE hintingPreferenceToRenderingMode(const QFontDef &fontDef)
+DWRITE_RENDERING_MODE QWindowsFontEngineDirectWrite::hintingPreferenceToRenderingMode(const QFontDef &fontDef) const
 {
+    if ((fontDef.styleStrategy & QFont::NoAntialias) && glyphFormat != QFontEngine::Format_ARGB)
+        return DWRITE_RENDERING_MODE_ALIASED;
+
     QFont::HintingPreference hintingPreference = QFont::HintingPreference(fontDef.hintingPreference);
     if (QHighDpiScaling::isActive() && hintingPreference == QFont::PreferDefaultHinting) {
         // Microsoft documentation recommends using asymmetric rendering for small fonts
@@ -480,7 +483,8 @@ void QWindowsFontEngineDirectWrite::recalcAdvances(QGlyphLayout *glyphs, QFontEn
     DWRITE_RENDERING_MODE renderMode = hintingPreferenceToRenderingMode(fontDef);
     bool needsDesignMetrics = shaperFlags & QFontEngine::DesignMetrics;
     if (!needsDesignMetrics && (renderMode == DWRITE_RENDERING_MODE_GDI_CLASSIC
-                             || renderMode == DWRITE_RENDERING_MODE_GDI_NATURAL)) {
+                             || renderMode == DWRITE_RENDERING_MODE_GDI_NATURAL
+                             || renderMode == DWRITE_RENDERING_MODE_ALIASED)) {
         hr = m_directWriteFontFace->GetGdiCompatibleGlyphMetrics(float(fontDef.pixelSize),
                                                                  1.0f,
                                                                  NULL,
@@ -667,7 +671,8 @@ QImage QWindowsFontEngineDirectWrite::alphaMapForGlyph(glyph_t glyph,
 
 bool QWindowsFontEngineDirectWrite::supportsHorizontalSubPixelPositions() const
 {
-    return true;
+    DWRITE_RENDERING_MODE renderMode = hintingPreferenceToRenderingMode(fontDef);
+    return renderMode != DWRITE_RENDERING_MODE_ALIASED;
 }
 
 QFontEngine::Properties QWindowsFontEngineDirectWrite::properties() const
@@ -770,7 +775,10 @@ QImage QWindowsFontEngineDirectWrite::imageForGlyph(glyph_t t,
 
     if (SUCCEEDED(hr)) {
         RECT rect;
-        glyphAnalysis->GetAlphaTextureBounds(DWRITE_TEXTURE_CLEARTYPE_3x1, &rect);
+        glyphAnalysis->GetAlphaTextureBounds(renderMode == DWRITE_RENDERING_MODE_ALIASED
+                                                ? DWRITE_TEXTURE_ALIASED_1x1
+                                                : DWRITE_TEXTURE_CLEARTYPE_3x1,
+                                             &rect);
 
         if (rect.top == rect.bottom || rect.left == rect.right)
             return QImage();
@@ -851,7 +859,8 @@ QImage QWindowsFontEngineDirectWrite::imageForGlyph(glyph_t t,
                                    b,
                                    a,
                                    colorGlyphsAnalysis,
-                                   boundingRect);
+                                   boundingRect,
+                                   renderMode);
                 }
                 colorGlyphsAnalysis->Release();
 
@@ -878,7 +887,8 @@ QImage QWindowsFontEngineDirectWrite::imageForGlyph(glyph_t t,
                            b,
                            a,
                            glyphAnalysis,
-                           boundingRect);
+                           boundingRect,
+                           renderMode);
         }
 
         glyphAnalysis->Release();
@@ -896,7 +906,8 @@ void QWindowsFontEngineDirectWrite::renderGlyphRun(QImage *destination,
                                                    float b,
                                                    float a,
                                                    IDWriteGlyphRunAnalysis *glyphAnalysis,
-                                                   const QRect &boundingRect)
+                                                   const QRect &boundingRect,
+                                                   DWRITE_RENDERING_MODE renderMode)
 {
     const int width = destination->width();
     const int height = destination->height();
@@ -917,12 +928,14 @@ void QWindowsFontEngineDirectWrite::renderGlyphRun(QImage *destination,
         BYTE *alphaValues = alphaValueArray.data();
         memset(alphaValues, 0, size);
 
-        HRESULT hr = glyphAnalysis->CreateAlphaTexture(DWRITE_TEXTURE_CLEARTYPE_3x1,
+        HRESULT hr = glyphAnalysis->CreateAlphaTexture(renderMode == DWRITE_RENDERING_MODE_ALIASED
+                                                               ? DWRITE_TEXTURE_ALIASED_1x1
+                                                               : DWRITE_TEXTURE_CLEARTYPE_3x1,
                                                        &rect,
                                                        alphaValues,
                                                        size);
         if (SUCCEEDED(hr)) {
-            if (destination->hasAlphaChannel()) {
+            if (destination->hasAlphaChannel()) { // Color glyphs
                 for (int y = 0; y < height; ++y) {
                     uint *dest = reinterpret_cast<uint *>(destination->scanLine(y));
                     BYTE *src = alphaValues + width * 3 * y;
@@ -940,7 +953,16 @@ void QWindowsFontEngineDirectWrite::renderGlyphRun(QImage *destination,
                                         qRound(qAlpha(currentRgb) * (1.0 - averageAlpha) + averageAlpha * 255));
                     }
                 }
+            } else if (renderMode == DWRITE_RENDERING_MODE_ALIASED) {
+                for (int y = 0; y < height; ++y) {
+                    uint *dest = reinterpret_cast<uint *>(destination->scanLine(y));
+                    BYTE *src = alphaValues + width * y;
 
+                    for (int x = 0; x < width; ++x) {
+                        int alpha = *(src++);
+                        dest[x] = (alpha << 16) + (alpha << 8) + alpha;
+                    }
+                }
             } else {
                 for (int y = 0; y < height; ++y) {
                     uint *dest = reinterpret_cast<uint *>(destination->scanLine(y));
@@ -1094,7 +1116,7 @@ glyph_metrics_t QWindowsFontEngineDirectWrite::alphaMapBoundingBox(glyph_t glyph
 
     if (SUCCEEDED(hr)) {
         RECT rect;
-        glyphAnalysis->GetAlphaTextureBounds(DWRITE_TEXTURE_CLEARTYPE_3x1, &rect);
+        glyphAnalysis->GetAlphaTextureBounds(renderMode == DWRITE_RENDERING_MODE_ALIASED ? DWRITE_TEXTURE_ALIASED_1x1 : DWRITE_TEXTURE_CLEARTYPE_3x1, &rect);
         glyphAnalysis->Release();
 
         int margin = glyphMargin(format);
diff --git a/src/gui/text/windows/qwindowsfontenginedirectwrite_p.h b/src/gui/text/windows/qwindowsfontenginedirectwrite_p.h
index f42894e394e..bef10f3dbef 100644
--- a/src/gui/text/windows/qwindowsfontenginedirectwrite_p.h
+++ b/src/gui/text/windows/qwindowsfontenginedirectwrite_p.h
@@ -22,6 +22,7 @@ QT_REQUIRE_CONFIG(directwrite);
 
 #include <QtGui/private/qfontengine_p.h>
 #include <QtCore/QSharedPointer>
+#include <dwrite.h>
 
 struct IDWriteFont;
 struct IDWriteFontFace;
@@ -108,8 +109,16 @@ private:
                          const QTransform &xform,
                          const QColor &color = QColor());
     void collectMetrics();
-    void renderGlyphRun(QImage *destination, float r, float g, float b, float a, IDWriteGlyphRunAnalysis *glyphAnalysis, const QRect &boundingRect);
+    void renderGlyphRun(QImage *destination,
+                        float r,
+                        float g,
+                        float b,
+                        float a,
+                        IDWriteGlyphRunAnalysis *glyphAnalysis,
+                        const QRect &boundingRect,
+                        DWRITE_RENDERING_MODE renderMode);
     static QString filenameFromFontFile(IDWriteFontFile *fontFile);
+    DWRITE_RENDERING_MODE hintingPreferenceToRenderingMode(const QFontDef &fontDef) const;
 
     const QSharedPointer<QWindowsFontEngineData> m_fontEngineData;