Use Lua string length instead of relying on `strlen` (#1262)

This allows us to render `NULL` byte sequences and not truncate strings 
that contain them.

src/api/renderer.c

@@ -193,7 +193,10 @@ static int f_font_gc(lua_State *L) {
 
 static int f_font_get_width(lua_State *L) {
   RenFont* fonts[FONT_FALLBACK_MAX]; font_retrieve(L, fonts, 1);
-  lua_pushnumber(L, ren_font_group_get_width(fonts, luaL_checkstring(L, 2)));
+  size_t len;
+  const char *text = luaL_checklstring(L, 2, &len);
+
+  lua_pushnumber(L, ren_font_group_get_width(fonts, text, len));
   return 1;
 }
 
@@ -338,11 +341,12 @@ static int f_draw_text(lua_State *L) {
   }
   lua_pop(L, 1);
 
-  const char *text = luaL_checkstring(L, 2);
+  size_t len;
+  const char *text = luaL_checklstring(L, 2, &len);
   float x = luaL_checknumber(L, 3);
   int y = luaL_checknumber(L, 4);
   RenColor color = checkcolor(L, 5, 255);
-  x = rencache_draw_text(fonts, text, x, y, color);
+  x = rencache_draw_text(fonts, text, len, x, y, color);
   lua_pushnumber(L, x);
   return 1;
 }

src/rencache.c

@@ -39,6 +39,7 @@ typedef struct {
   RenColor color;
   RenFont *fonts[FONT_FALLBACK_MAX];
   float text_x;
+  size_t len;
   char text[];
 } Command;
 
@@ -145,12 +146,12 @@ void rencache_draw_rect(RenRect rect, RenColor color) {
   }
 }
 
-float rencache_draw_text(RenFont **fonts, const char *text, float x, int y, RenColor color)
+float rencache_draw_text(RenFont **fonts, const char *text, size_t len, float x, int y, RenColor color)
 {
-  float width = ren_font_group_get_width(fonts, text);
+  float width = ren_font_group_get_width(fonts, text, len);
   RenRect rect = { x, y, (int)width, ren_font_group_get_height(fonts) };
   if (rects_overlap(screen_rect, rect)) {
-    int sz = strlen(text) + 1;
+    int sz = len + 1;
     Command *cmd = push_command(DRAW_TEXT, COMMAND_BARE_SIZE + sz);
     if (cmd) {
       memcpy(cmd->text, text, sz);
@@ -158,6 +159,7 @@ float rencache_draw_text(RenFont **fonts, const char *text, float x, int y, RenC
       memcpy(cmd->fonts, fonts, sizeof(RenFont*)*FONT_FALLBACK_MAX);
       cmd->rect = rect;
       cmd->text_x = x;
+      cmd->len = len;
       cmd->tab_size = ren_font_group_get_tab_size(fonts);
     }
   }
@@ -266,7 +268,7 @@ void rencache_end_frame() {
           break;
         case DRAW_TEXT:
           ren_font_group_set_tab_size(cmd->fonts, cmd->tab_size);
-          ren_draw_text(cmd->fonts, cmd->text, cmd->text_x, cmd->rect.y, cmd->color);
+          ren_draw_text(cmd->fonts, cmd->text, cmd->len, cmd->text_x, cmd->rect.y, cmd->color);
           break;
       }
     }

src/rencache.h

@@ -8,7 +8,7 @@
 void  rencache_show_debug(bool enable);
 void  rencache_set_clip_rect(RenRect rect);
 void  rencache_draw_rect(RenRect rect, RenColor color);
-float rencache_draw_text(RenFont **font, const char *text, float x, int y, RenColor color);
+float rencache_draw_text(RenFont **font, const char *text, size_t len, float x, int y, RenColor color);
 void  rencache_invalidate(void);
 void  rencache_begin_frame();
 void  rencache_end_frame();

src/renderer.c

@@ -358,9 +358,9 @@ int ren_font_group_get_height(RenFont **fonts) {
   return fonts[0]->height;
 }
 
-float ren_font_group_get_width(RenFont **fonts, const char *text) {
+float ren_font_group_get_width(RenFont **fonts, const char *text, size_t len) {
   float width = 0;
-  const char* end = text + strlen(text);
+  const char* end = text + len;
   GlyphMetric* metric = NULL; GlyphSet* set = NULL;
   while (text < end) {
     unsigned int codepoint;
@@ -374,7 +374,7 @@ float ren_font_group_get_width(RenFont **fonts, const char *text) {
   return width / surface_scale;
 }
 
-float ren_draw_text(RenFont **fonts, const char *text, float x, int y, RenColor color) {
+float ren_draw_text(RenFont **fonts, const char *text, size_t len, float x, int y, RenColor color) {
   SDL_Surface *surface = renwin_get_surface(&window_renderer);
   const RenRect clip = window_renderer.clip;
 
@@ -382,7 +382,7 @@ float ren_draw_text(RenFont **fonts, const char *text, float x, int y, RenColor
   float pen_x = x * surface_scale;
   y *= surface_scale;
   int bytes_per_pixel = surface->format->BytesPerPixel;
-  const char* end = text + strlen(text);
+  const char* end = text + len;
   uint8_t* destination_pixels = surface->pixels;
   int clip_end_x = clip.x + clip.width, clip_end_y = clip.y + clip.height;
 

src/renderer.h

@@ -28,8 +28,8 @@ int ren_font_group_get_height(RenFont **font);
 float ren_font_group_get_size(RenFont **font);
 void ren_font_group_set_size(RenFont **font, float size);
 void ren_font_group_set_tab_size(RenFont **font, int n);
-float ren_font_group_get_width(RenFont **font, const char *text);
+float ren_font_group_get_width(RenFont **font, const char *text, size_t len);
-float ren_draw_text(RenFont **font, const char *text, float x, int y, RenColor color);
+float ren_draw_text(RenFont **font, const char *text, size_t len, float x, int y, RenColor color);
 
 void ren_draw_rect(RenRect rect, RenColor color);