Add video mode switcher to handle logical sizes

include/apple2.h

@@ -5,6 +5,13 @@
 #include "mos6502.h"
 #include "vm_screen.h"
 
+enum video_modes {
+    VIDEO_LORES,
+    VIDEO_HIRES,
+    VIDEO_DOUBLE_LORES,
+    VIDEO_DOUBLE_HIRES,
+};
+
 typedef struct {
     /*
      * The apple 2 hardware used an MOS-6502 processor.
@@ -23,6 +30,13 @@ typedef struct {
      */
     vm_screen *screen;
 
+    /*
+     * This is the mode in which we must interpret graphics. This will
+     * tell us not only if we're in lo- or hi-res, but also if we are in
+     * single or double view mode.
+     */
+    int video_mode;
+
     /*
      * Our two disk drives.
      */
@@ -37,5 +51,6 @@ extern void apple2_clear_strobe(apple2 *);
 extern void apple2_release_key(apple2 *);
 extern int apple2_boot(apple2 *);
 extern void apple2_run_loop(apple2 *);
+extern void apple2_set_video(apple2 *, int);
 
 #endif

src/apple2.c

@@ -156,3 +156,28 @@ apple2_boot(apple2 *mach)
 
     return OK;
 }
+
+void
+apple2_set_video(apple2 *mach, int mode)
+{
+    int width, height;
+
+    mach->video_mode = mode;
+
+    // In the traditional video modes that Apple II first came in, you
+    // would have a maximum width of 280 pixels. (In lo-res, you have
+    // fewer pixels, but that is something we have to handle in our
+    // drawing functions rather than by changing the logical size.)
+    width = 280;
+    height = 192;
+
+    // In double video modes, the width is effectively doubled, but the
+    // height is untouched.
+    if (mach->video_mode == VIDEO_DOUBLE_LORES ||
+        mach->video_mode == VIDEO_DOUBLE_HIRES
+       ) {
+        width = 560;
+    }
+
+    vm_screen_set_logical_coords(mach->screen, width, height);
+}