Make the FontRenderer's Bitmap struct opaque outside the library

lib/font_renderer/font_renderer.cpp

@@ -7,8 +7,29 @@
 
 #include "font_renderer_alpha.h"
 
+// Important: when a subpixel scale is used the width below will be the width in logical pixel.
+// As each logical pixel contains 3 subpixels it means that the 'pixels' pointer
+// will hold enough space for '3 * width' uint8_t values.
+struct FontRendererBitmap {
+  agg::int8u *pixels;
+  int width, height;
+};
+
 typedef agg::blender_rgb_gamma<agg::rgba8, agg::order_bgra, agg::gamma_lut<> > blender_gamma_type;
 
+FontRendererBitmap* FontRendererBitmapNew(int width, int height, int subpixel_scale) {
+    FontRendererBitmap *image = (FontRendererBitmap *) malloc(sizeof(FontRendererBitmap) + width * height * subpixel_scale);
+    if (!image) { return NULL; }
+    image->pixels = (agg::int8u *) (image + 1);
+    image->width = width;
+    image->height = height;
+    return image;
+}
+
+void FontRendererBitmapFree(FontRendererBitmap *image) {
+  free(image);
+}
+
 class FontRendererImpl {
 public:
     // Conventional LUT values: (1./3., 2./9., 1./9.)
@@ -149,11 +170,14 @@ static int ceil_to_multiple(int n, int p) {
 }
 
 int FontRendererBakeFontBitmap(FontRenderer *font_renderer, int font_height,
-    void *pixels, int pixels_width, int pixels_height,
+    FontRendererBitmap *image,
     int first_char, int num_chars, GlyphBitmapInfo *glyphs, int subpixel_scale)
 {
     font_renderer_alpha& renderer_alpha = font_renderer->renderer_alpha();
 
+    agg::int8u *pixels = image->pixels;
+    const int pixels_width = image->width, pixels_height = image->height;
+
     const int pixel_size = 1;
     memset(pixels, 0x00, pixels_width * pixels_height * subpixel_scale * pixel_size);
 
@@ -167,7 +191,7 @@ int FontRendererBakeFontBitmap(FontRenderer *font_renderer, int font_height,
     const int y_step = font_height + 2 * pad_y;
 
     agg::lcd_distribution_lut& lcd_lut = font_renderer->lcd_distribution_lut();
-    agg::rendering_buffer ren_buf((agg::int8u *) pixels, pixels_width * subpixel_scale, pixels_height, -pixels_width * subpixel_scale * pixel_size);
+    agg::rendering_buffer ren_buf(pixels, pixels_width * subpixel_scale, pixels_height, -pixels_width * subpixel_scale * pixel_size);
     // When using subpixel font rendering it is needed to leave a padding pixel on the left and on the right.
     // Since each pixel is composed by n subpixel we set below x_start to subpixel_scale instead than zero.
     const int x_start = subpixel_scale;

lib/font_renderer/font_renderer.h

@@ -12,13 +12,7 @@ typedef struct {
   float xoff, yoff, xadvance;
 } GlyphBitmapInfo;
 
-// Important: when a subpixel scale is used the width below will be the width in logical pixel.
+typedef struct FontRendererBitmap FontRendererBitmap;
-// As each logical pixel contains 3 subpixels it means that the 'pixels' pointer
-// will hold enough space for '3 * width' uint8_t values.
-typedef struct {
-  uint8_t *pixels;
-  int width, height;
-} FontRendererBitmap;
 
 struct FontRendererImpl;
 typedef struct FontRendererImpl FontRenderer;
@@ -46,7 +40,7 @@ int             FontRendererLoadFont(FontRenderer *, const char *filename);
 int             FontRendererGetFontHeight(FontRenderer *, float size);
 
 int             FontRendererBakeFontBitmap(FontRenderer *, int font_height,
-                    void *pixels, int pixels_width, int pixels_height,
+                    FontRendererBitmap *image,
                     int first_char, int num_chars, GlyphBitmapInfo *glyph_info,
                     int subpixel_scale);
 
@@ -65,6 +59,10 @@ void            FontRendererBlendGammaSubpixel(FontRenderer *font_renderer,
                     const FontRendererBitmap *glyphs_bitmap,
                     const GlyphBitmapInfo *glyph, FontRendererColor color);
 
+FontRendererBitmap* FontRendererBitmapNew(int width, int height, int subpixel_scale);
+
+void FontRendererBitmapFree(FontRendererBitmap *image);
+
 #ifdef __cplusplus
 }
 #endif

src/renderer.c

@@ -104,21 +104,6 @@ void ren_free_image(RenImage *image) {
   free(image);
 }
 
-// FIXME: move this function into FontRenderer and change name.
-FontRendererBitmap* ren_new_coverage_image(int width, int height, int subpixel_scale) {
-  assert(width > 0 && height > 0);
-  FontRendererBitmap *image = malloc(sizeof(FontRendererBitmap) + width * height * subpixel_scale * sizeof(uint8_t));
-  check_alloc(image);
-  image->pixels = (void*) (image + 1);
-  image->width = width;
-  image->height = height;
-  return image;
-}
-
-void ren_free_coverage_image(FontRendererBitmap *image) {
-  free(image);
-}
-
 static GlyphSet* load_glyphset(RenFont *font, int idx) {
   GlyphSet *set = check_alloc(calloc(1, sizeof(GlyphSet)));
 
@@ -128,17 +113,17 @@ static GlyphSet* load_glyphset(RenFont *font, int idx) {
   int width = 128;
   int height = 128;
 retry:
-  set->image = ren_new_coverage_image(width, height, subpixel_scale);
+  set->image = FontRendererBitmapNew(width, height, subpixel_scale);
+  check_alloc(set->image);
 
   int res = FontRendererBakeFontBitmap(font->renderer, font->height,
-    (void *) set->image->pixels, width, height,
+    set->image, idx << 8, 256, set->glyphs, subpixel_scale);
-    idx << 8, 256, set->glyphs, subpixel_scale);
 
   /* retry with a larger image buffer if the buffer wasn't large enough */
   if (res < 0) {
     width *= 2;
     height *= 2;
-    ren_free_coverage_image(set->image);
+    FontRendererBitmapFree(set->image);
     goto retry;
   }
 
@@ -188,7 +173,7 @@ void ren_free_font(RenFont *font) {
   for (int i = 0; i < MAX_GLYPHSET; i++) {
     GlyphSet *set = font->sets[i];
     if (set) {
-      ren_free_coverage_image(set->image);
+      FontRendererBitmapFree(set->image);
       free(set);
     }
   }