mirror of https://github.com/pevans/erc-c.git
142 lines
4.1 KiB
C
142 lines
4.1 KiB
C
/*
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* vm_bitfont.c
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*
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* The bitfont code allows us to define and work with a bitmapped font.
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* You can find the bitmap font glyphs in the `/fonts` subdir within the
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* repository root, as well as bmp files that are compiled from those
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* glyphs (via `/tools/build-fonts`).
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*
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* We do not have support for truetype fonts (nor other types of fonts)
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* at this time, but the glyph system is pretty easy to work with, even
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* if it is a hack.
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*/
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#include "vm_bitfont.h"
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/*
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* Create a new bitfont from a given font name. This font name must
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* indicate something that exists in the filesystem relative to a point,
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* which means it must have been created during installation.
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*
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* This also indicates what the width and height of each glyph will be,
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* along with a character mask we will apply when figuring out where to
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* access bitmap data. (For example, if we only support 7-bit
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* characters, the cmask should limit us to 0-127 so that we can't
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* accidentally pass in a value that uses the 8th bit and crashes us
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* out.
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*/
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vm_bitfont *
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vm_bitfont_create(vm_screen *screen,
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const vm_8bit *fontdata, int fontsize,
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int width, int height, char cmask)
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{
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SDL_Surface *surf;
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SDL_RWops *rw;
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vm_bitfont *font;
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// Build the RWops object from the given fontdata; we have to use
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// FromConstMem because we passed a const pointer into this
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// function.
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rw = SDL_RWFromConstMem(fontdata, fontsize);
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if (rw == NULL) {
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log_crit("Failed to create RWops from font data: %s",
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SDL_GetError());
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return NULL;
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}
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// And here we build a surface from the RWops, which is a nifty way
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// of getting a bitmap from memory rather than loading from a file.
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surf = SDL_LoadBMP_RW(rw, 0);
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if (surf == NULL) {
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log_crit("Failed to create bitmap from RWops: %s",
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SDL_GetError());
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return NULL;
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}
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font = malloc(sizeof(vm_bitfont));
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if (font == NULL) {
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log_crit("Could not allocate memory for font");
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return NULL;
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}
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// The texture is what we can use to blit onto the renderer
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font->texture = SDL_CreateTextureFromSurface(screen->render, surf);
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font->width = width;
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font->height = height;
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font->cmask = cmask;
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return font;
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}
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/*
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* This just frees the memory for the font.
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*/
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void
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vm_bitfont_free(vm_bitfont *font)
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{
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SDL_DestroyTexture(font->texture);
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free(font);
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}
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/*
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* This function will provide the correct offset within the bitmap data
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* where you can find the glyph that matches the given character.
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* Because we want to note both an x and a y coordinate, we require
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* pointers to those, which we simply dereference to assign the right
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* value.
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*/
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void
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vm_bitfont_offset(vm_bitfont *font, char ch, vm_area *area)
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{
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int row = (ch & 0xf0) >> 4;
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int col = ch & 0x0f;
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area->xoff = col * font->width;
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area->yoff = row * font->height;
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}
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/*
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* Render the given character, in the given font, on the given screen at
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* the given destination.
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*/
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int
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vm_bitfont_render(vm_bitfont *font,
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vm_screen *screen,
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vm_area *dest,
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char ch)
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{
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vm_area src;
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// Our bitmap font may not be able to support all 256 possible
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// values that a character can hold; the cmask will limit us to
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// what's safe to query in the bitmap.
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ch = ch & font->cmask;
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// The width and height of the glyph are as indicated by the font
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// struct
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src.width = font->width;
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src.height = font->height;
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// Get the spot in the bitmap where the glyph is found
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vm_bitfont_offset(font, ch, &src);
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// Bring the destination attributes into the SDL_Rect we need to
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// pass into SDL_RenderCopy(). Also bring in the src attributes
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// we've built earlier.
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MAKE_SDL_RECT(dest_rect, *dest);
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MAKE_SDL_RECT(src_rect, src);
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if (screen->render) {
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if (SDL_RenderCopy(screen->render, font->texture,
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&src_rect, &dest_rect) < 0
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) {
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log_crit("Failed to render glyph: %s", SDL_GetError());
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return ERR_GFXOP;
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}
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}
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screen->dirty = true;
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return OK;
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}
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