Adopt flat layer command buffers, float geometry

By preallocating a big flat command buffer for each layer that stores
each draw command in sequence we can get rid of some of the pointer
chasing of the pool of separate draw commands, instead reading data
sequentially from the stream of draw commands.

The stream can be walked from front to back by skipping ahead by the
computed size of each command.

While making these changes the underlying floating point type for vertex
positions and texcoords was changed from doubles to floats to save
significant storage space each frame.

Author: zao

engine/render/r_font.cpp

@@ -17,10 +17,10 @@
 
 // Glyph parameters
 struct f_glyph_s {
-	double	tcLeft = 0.0;
-	double	tcRight = 0.0;
-	double	tcTop = 0.0;
-	double	tcBottom = 0.0;
+	float	tcLeft = 0.0;
+	float	tcRight = 0.0;
+	float	tcTop = 0.0;
+	float	tcBottom = 0.0;
 	int		width = 0;
 	int		spLeft = 0;
 	int		spRight = 0;
@@ -32,7 +32,7 @@ struct f_fontHeight_s {
 	int		height;
 	int		numGlyph;
 	f_glyph_s glyphs[128];
-	f_glyph_s defGlyph{0.0, 0.0, 0.0, 0.0, 0, 0, 0};
+	f_glyph_s defGlyph{0.0f, 0.0f, 0.0f, 0.0f, 0, 0, 0};
 
 	f_glyph_s const& Glyph(char ch) const {
 		if ((unsigned char)ch >= numGlyph) {
@@ -84,10 +84,10 @@ r_font_c::r_font_c(r_renderer_c* renderer, const char* fontName)
 			// Add glyph
 			if (fh->numGlyph >= 128) continue;
 			f_glyph_s* glyph = &fh->glyphs[fh->numGlyph++];
-			glyph->tcLeft = (double)x / fh->tex->fileWidth;
-			glyph->tcRight = (double)(x + w) / fh->tex->fileWidth;
-			glyph->tcTop = (double)y / fh->tex->fileHeight;
-			glyph->tcBottom = (double)(y + fh->height) / fh->tex->fileHeight;
+			glyph->tcLeft = (float)x / fh->tex->fileWidth;
+			glyph->tcRight = (float)(x + w) / fh->tex->fileWidth;
+			glyph->tcTop = (float)y / fh->tex->fileHeight;
+			glyph->tcBottom = (float)(y + fh->height) / fh->tex->fileHeight;
 			glyph->width = w;
 			glyph->spLeft = sl;
 			glyph->spRight = sr;
@@ -240,14 +240,14 @@ void r_font_c::DrawTextLine(scp_t pos, int align, int height, col4_t col, const
 
 	// Find best height to use
 	f_fontHeight_s *fh = fontHeights[height > maxHeight? (numFontHeight - 1) : fontHeightMap[height]];
-	double scale = (double)height / fh->height;
+	float scale = (float)height / fh->height;
 
 	// Calculate the string position
-	double x = pos[X];
-	double y = pos[Y];
+	float x = pos[X];
+	float y = pos[Y];
 	if (align != F_LEFT) {
 		// Calculate the real width of the string
-		double width = StringWidthInternal(fh, str) * scale;
+		float width = StringWidthInternal(fh, str) * scale;
 		switch (align) {
 		case F_CENTRE:
 			x = floor((renderer->VirtualScreenWidth() - width) / 2.0f + pos[X]);
@@ -297,7 +297,7 @@ void r_font_c::DrawTextLine(scp_t pos, int align, int height, col4_t col, const
 		auto& glyph = fh->Glyph(*str++);
 		x+= glyph.spLeft * scale;
 		if (glyph.width) {
-			double w = glyph.width * scale;
+			float w = glyph.width * scale;
 			if (x + w >= 0 && x < renderer->VirtualScreenWidth()) {
 				renderer->curLayer->Quad(
 					glyph.tcLeft, glyph.tcTop, x, y,