Add support for vm_bitfont

CMakeLists.txt

@@ -32,6 +32,8 @@ include_directories(include /usr/local/include ${sdl_headers})
 
 link_directories(/usr/local/lib)
 
+add_definitions(-DINSTALL_PATH="../")
+
 # our bullshit
 add_executable(erc ${sources} src/main.c)
 

include/log.h

@@ -13,6 +13,7 @@ enum log_errcode {
     ERR_OOB,            // out of bounds
     ERR_BADFILE,
     ERR_GFXINIT,        // couldn't initialize graphics
+    ERR_GFXOP,          // we couldn't execute a specific graphic operation
 };
 
 extern void log_write(int, const char *, ...);

include/vm_bitfont.h

@@ -0,0 +1,23 @@
+#ifndef _VM_BITFONT_H_
+#define _VM_BITFONT_H_
+
+#include <SDL.h>
+
+#include "log.h"
+#include "vm_screen.h"
+
+typedef struct {
+    SDL_Texture *texture;
+
+    int width;
+    int height;
+
+    char cmask;
+} vm_bitfont;
+
+extern vm_bitfont *vm_bitfont_create(vm_screen *, const char *, int, int, char);
+extern void vm_bitfont_free(vm_bitfont *);
+extern void vm_bitfont_offset(vm_bitfont *, char, int *, int *);
+extern int vm_bitfont_render(vm_bitfont *, vm_screen *, SDL_Rect *, char);
+
+#endif

sources.cmake

@@ -11,6 +11,7 @@ set(erc_sources
 	mos6502.loadstor.c
 	mos6502.stat.c
 	option.c
+	vm_bitfont.c
 	vm_screen.c
 	vm_segment.c
 	)

src/vm_bitfont.c

@@ -0,0 +1,110 @@
+/*
+ * vm_bitfont.c
+ */
+
+#include "vm_bitfont.h"
+
+/*
+ * Create a new bitfont from a given font name. This font name must
+ * indicate something that exists in the filesystem relative to a point,
+ * which means it must have been created during installation.
+ *
+ * This also indicates what the width and height of each glyph will be,
+ * along with a character mask we will apply when figuring out where to
+ * access bitmap data. (For example, if we only support 7-bit
+ * characters, the cmask should limit us to 0-127 so that we can't
+ * accidentally pass in a value that uses the 8th bit and crashes us
+ * out.
+ */
+vm_bitfont *
+vm_bitfont_create(vm_screen *screen, 
+                  const char *from_name, 
+                  int width, 
+                  int height,
+                  char cmask)
+{
+    SDL_Surface *surf;
+    vm_bitfont *font;
+    char namebuf[1024];
+
+    font = malloc(sizeof(vm_bitfont));
+    if (font == NULL) {
+        log_critical("Could not allocate memory for font");
+        return NULL;
+    }
+
+    snprintf(namebuf, 
+             sizeof(namebuf) - 1, 
+             "%s/fonts/%s.bmp",
+             INSTALL_PATH, from_name);
+
+    // FIXME: test if this even works... fail if not
+    surf = SDL_LoadBMP(namebuf);
+
+    font->texture = SDL_CreateTextureFromSurface(screen->render, surf);
+    font->width = width;
+    font->height = height;
+    font->cmask = cmask;
+
+    return font;
+}
+
+/*
+ * This just frees the memory for the font.
+ */
+void
+vm_bitfont_free(vm_bitfont *font)
+{
+    SDL_DestroyTexture(font->texture);
+    free(font);
+}
+
+/*
+ * This function will provide the correct offset within the bitmap data
+ * where you can find the glyph that matches the given character.
+ * Because we want to note both an x and a y coordinate, we require
+ * pointers to those, which we simply dereference to assign the right
+ * value.
+ */
+void
+vm_bitfont_offset(vm_bitfont *font, char ch, int *xcoord, int *ycoord)
+{
+    int row = (ch & 0xf0) >> 4;
+    int col = ch & 0x0f;
+
+    *xcoord = col * font->width;
+    *ycoord = row * font->height;
+}
+
+/*
+ * Render the given character, in the given font, on the given screen at
+ * the given destination.
+ */
+int
+vm_bitfont_render(vm_bitfont *font, 
+                  vm_screen *screen, 
+                  SDL_Rect *dest, 
+                  char ch)
+{
+    SDL_Rect src;
+
+    // Our bitmap font may not be able to support all 256 possible
+    // values that a character can hold; the cmask will limit us to
+    // what's safe to query in the bitmap.
+    ch = ch & font->cmask;
+
+    // The width and height of the glyph are as indicated by the font
+    // struct
+    src.w = font->width;
+    src.h = font->height;
+
+    // Get the spot in the bitmap where the glyph is found
+    vm_bitfont_offset(font, ch, &src.x, &src.y);
+
+    if (SDL_RenderCopy(screen->render, font->texture, dest, &src) < 0) {
+        log_critical("Failed to render glyph: %s", SDL_GetError());
+        return ERR_GFXOP;
+    }
+
+    return OK;
+}

tests/CMakeLists.txt

@@ -36,6 +36,8 @@ endforeach(src)
 # make any particular effort to include it in add_executable().
 file(GLOB test_sources "*.c")
 
+add_definitions(-DINSTALL_PATH="../../")
+
 add_executable(erc-test ${sources} ${test_sources})
 
 # Our unit-testing library