app_server: Implemented support for B_CHAR_SPACING.

It doesn't yield quiet the expected results, yet. When hinting is turned on,
FontEngine takes a measurement of the precise advance values for each
cached glyph by invoking FT_Load_Glyph() with the FT_LOAD_NO_HINTING flag,
before loading the glyph for real without that flag. In GlyphLayoutEngine.h,
the precise advance value is used for B_CHAR_SPACING. The intended result
is that glyphs are rendered hinted (according to global Appearance settings),
but spaced along the base-line with precise, unhinted advance values. An
application would use this for example to implement precise page or print
preview and also for zooming text without altering the placement of glyphs.
For Gobe Productive, problems can be observed, because we don't implement this
correctly, yet.

src/servers/app/font/FontCacheEntry.cpp

@@ -96,14 +96,16 @@ public:
 
 	GlyphCache* CacheGlyph(uint32 glyphIndex,
 		uint32 dataSize, glyph_data_type dataType, const agg::rect_i& bounds,
-		float advanceX, float advanceY, float insetLeft, float insetRight)
+		float advanceX, float advanceY, float preciseAdvanceX,
+		float preciseAdvanceY, float insetLeft, float insetRight)
 	{
 		GlyphCache* glyph = fGlyphTable.Lookup(glyphIndex);
 		if (glyph != NULL)
 			return NULL;
 
 		glyph = new(std::nothrow) GlyphCache(glyphIndex, dataSize, dataType,
-			bounds, advanceX, advanceY, insetLeft, insetRight);
+			bounds, advanceX, advanceY, preciseAdvanceX, preciseAdvanceY,
+			insetLeft, insetRight);
 		if (glyph == NULL || glyph->data == NULL) {
 			delete glyph;
 			return NULL;
@@ -293,7 +295,7 @@ FontCacheEntry::CreateGlyph(uint32 glyphCode, FontCacheEntry* fallbackEntry)
 		if (render_as_zero_width(glyphCode)) {
 			// cache and return a zero width glyph
 			return fGlyphCache->CacheGlyph(glyphCode, 0, glyph_data_invalid,
-				agg::rect_i(0, 0, -1, -1), 0, 0, 0, 0);
+				agg::rect_i(0, 0, -1, -1), 0, 0, 0, 0, 0, 0);
 		}
 
 		// reset to our engine
@@ -310,6 +312,7 @@ FontCacheEntry::CreateGlyph(uint32 glyphCode, FontCacheEntry* fallbackEntry)
 		glyph = fGlyphCache->CacheGlyph(glyphCode,
 			engine->DataSize(), engine->DataType(), engine->Bounds(),
 			engine->AdvanceX(), engine->AdvanceY(),
+			engine->PreciseAdvanceX(), engine->PreciseAdvanceY(),
 			engine->InsetLeft(), engine->InsetRight());
 
 		if (glyph != NULL)
@@ -326,7 +329,7 @@ FontCacheEntry::InitAdaptors(const GlyphCache* glyph,
 	GlyphGray8Adapter& gray8Adapter, GlyphPathAdapter& pathAdapter,
 	double scale)
 {
-	if (!glyph)
+	if (glyph == NULL)
 		return;
 
 	switch(glyph->data_type) {

src/servers/app/font/FontCacheEntry.h

@@ -43,6 +43,7 @@
 struct GlyphCache {
 	GlyphCache(uint32 glyphIndex, uint32 dataSize, glyph_data_type dataType,
 			const agg::rect_i& bounds, float advanceX, float advanceY,
+			float preciseAdvanceX, float preciseAdvanceY,
 			float insetLeft, float insetRight)
 		:
 		glyph_index(glyphIndex),
@@ -52,6 +53,8 @@ struct GlyphCache {
 		bounds(bounds),
 		advance_x(advanceX),
 		advance_y(advanceY),
+		precise_advance_x(preciseAdvanceX),
+		precise_advance_y(preciseAdvanceY),
 		inset_left(insetLeft),
 		inset_right(insetRight),
 		hash_link(NULL)
@@ -70,6 +73,8 @@ struct GlyphCache {
 	agg::rect_i		bounds;
 	float			advance_x;
 	float			advance_y;
+	float			precise_advance_x;
+	float			precise_advance_y;
 	float			inset_left;
 	float			inset_right;
 

src/servers/app/font/FontEngine.cpp

@@ -624,7 +624,22 @@ FontEngine::PrepareGlyph(uint32 glyphIndex)
 	loadFlags |= fGlyphRendering == glyph_ren_subpix ?
 		FT_LOAD_TARGET_LCD : FT_LOAD_TARGET_NORMAL;
 
-	fLastError = FT_Load_Glyph(fFace, glyphIndex, loadFlags);
+	if (fHinting) {
+		// Load without hinting to get precise advance values
+		// for B_CHAR_SPACING
+		fLastError = FT_Load_Glyph(fFace, glyphIndex, loadFlags
+			| FT_LOAD_NO_HINTING);
+	} else {
+		fLastError = FT_Load_Glyph(fFace, glyphIndex, loadFlags);
+	}
+
+	fPreciseAdvanceX = int26p6_to_dbl(fFace->glyph->advance.x);
+	fPreciseAdvanceY = int26p6_to_dbl(fFace->glyph->advance.y);
+
+	if (fHinting) {
+		// Need to load again with hinting.
+		fLastError = FT_Load_Glyph(fFace, glyphIndex, loadFlags);
+	}
 
 	if (fLastError != 0)
 		return false;

src/servers/app/font/FontEngine.h

@@ -105,6 +105,10 @@ class FontEngine {
 									{ return fAdvanceX; }
 			double				AdvanceY() const
 									{ return fAdvanceY; }
+			double				PreciseAdvanceX() const
+									{ return fPreciseAdvanceX; }
+			double				PreciseAdvanceY() const
+									{ return fPreciseAdvanceY; }
 			double				InsetLeft() const
 									{ return fInsetLeft; }
 			double				InsetRight() const
@@ -136,6 +140,8 @@ class FontEngine {
 			agg::rect_i			fBounds;
 			double				fAdvanceX;
 			double				fAdvanceY;
+			double				fPreciseAdvanceX;
+			double				fPreciseAdvanceY;
 			double				fInsetLeft;
 			double				fInsetRight;
 

src/servers/app/font/GlyphLayoutEngine.h

@@ -253,8 +253,13 @@ GlyphLayoutEngine::LayoutGlyphs(GlyphConsumer& consumer,
 			advanceY = 0;
 		} else {
 			// get next increment for pen position
-			advanceX = glyph->advance_x;
-			advanceY = glyph->advance_y;
+			if (spacing == B_CHAR_SPACING) {
+				advanceX = glyph->precise_advance_x;
+				advanceY = glyph->precise_advance_y;
+			} else {
+				advanceX = glyph->advance_x;
+				advanceY = glyph->advance_y;
+			}
 
 			// adjust for custom spacing
 			if (delta != NULL) {