Rework screen display logic for more efficiency

include/vm_screen.h

@@ -38,9 +38,16 @@ typedef struct {
     vm_8bit last_key;
     bool key_pressed;
 
+    /*
+     * Is the screen dirty? That is to say, has something about it
+     * changed that now requires we redraw the screen?
+     */
+    bool dirty;
+
 } vm_screen;
 
 extern bool vm_screen_active(vm_screen *);
+extern bool vm_screen_dirty(vm_screen *);
 extern bool vm_screen_key_pressed(vm_screen *);
 extern char vm_screen_last_key(vm_screen *);
 extern int vm_screen_add_window(vm_screen *, int, int);

src/apple2.bank.c

@@ -223,7 +223,6 @@ SEGMENT_READER(apple2_bank_switch_read)
                 : 0x00;
     }
 
-    log_critical("; bank_switch = %x", mach->bank_switch);
     return 0;
 }
 
@@ -248,6 +247,4 @@ SEGMENT_WRITER(apple2_bank_switch_write)
                                    mach->bank_switch & ~BANK_ALTZP);
             break;
     }
-
-    log_critical("; bank_switch = %x", mach->bank_switch);
 }

src/apple2.c

@@ -322,10 +322,12 @@ apple2_run_loop(apple2 *mach)
     }
 
     while (vm_screen_active(mach->screen)) {
-        mos6502_dis_opcode(mach->cpu, stdout, mach->cpu->PC);
+        //mos6502_dis_opcode(mach->cpu, stdout, mach->cpu->PC);
         mos6502_execute(mach->cpu);
-//        apple2_draw_40col(mach);
+
-//        vm_screen_refresh(mach->screen);
+        if (vm_screen_dirty(mach->screen)) {
+            vm_screen_refresh(mach->screen);
+        }
     }
 }
 

src/apple2.dbuf.c

@@ -3,6 +3,7 @@
  */
 
 #include "apple2.dbuf.h"
+#include "apple2.draw.h"
 
 static size_t switch_reads[] = {
     0xC01A,
@@ -91,6 +92,12 @@ SEGMENT_WRITER(apple2_dbuf_write)
     // Again, segment is allowed to be that which was passed in if
     // 80STORE is low. 
     segment->memory[addr] = value;
+
+    if (mach->display_mode & DISPLAY_TEXT) {
+        apple2_draw_40col(mach);
+    } else {
+        apple2_draw_40col(mach);
+    }
 }
 
 /*
@@ -213,8 +220,6 @@ SEGMENT_READER(apple2_dbuf_switch_read)
             break;
     }
 
-    log_critical("; display_mode = %x", mach->display_mode);
-
     // ???
     return 0;
 }
@@ -288,6 +293,4 @@ SEGMENT_WRITER(apple2_dbuf_switch_write)
                                mach->display_mode & ~DISPLAY_DHIRES);
             break;
     }
-
-    log_critical("; display_mode = %x", mach->display_mode);
 }

src/apple2.draw.c

@@ -88,10 +88,9 @@ apple2_draw_pixel_lores(apple2 *mach, vm_16bit addr)
 void
 apple2_draw_text(apple2 *mach, vm_16bit addr)
 {
-    vm_8bit lsb;
+    vm_8bit lsb, ch;
     vm_16bit page_base;
     vm_area dest;
-    char ch;
 
     // The text display buffers are located at "Page 1" and "Page 2",
     // which are at byte 1024-2047 (0x0400-0x07FF) and byte 2048-3071
@@ -151,7 +150,7 @@ apple2_draw_text(apple2 *mach, vm_16bit addr)
     dest.height = mach->sysfont->height;
 
     // And...lastly...what's in the address?
-    ch = (char)vm_segment_get(mach->main, addr);
+    ch = mos6502_get(mach->cpu, addr);
 
     // Let's firstly blank out that space on screen.
     vm_bitfont_render(mach->sysfont, mach->screen, &dest, ' ');

src/apple2.mem.c

@@ -214,8 +214,6 @@ SEGMENT_READER(apple2_mem_switch_read)
             break;
     }
 
-    log_critical("; memory_mode = %x", mach->memory_mode);
-
     // ???
     return 0;
 }
@@ -286,6 +284,4 @@ SEGMENT_WRITER(apple2_mem_switch_write)
             break;
 
     }
-
-    log_critical("; memory_mode = %x", mach->memory_mode);
 }

src/apple2.pc.c

@@ -187,6 +187,4 @@ SEGMENT_WRITER(apple2_pc_switch_write)
                                    mach->memory_mode & ~MEMORY_SLOTCXROM);
             break;
     }
-
-    log_critical("; memory_mode = %x", mach->memory_mode);
 }

src/vm_bitfont.c

@@ -123,5 +123,6 @@ vm_bitfont_render(vm_bitfont *font,
         return ERR_GFXOP;
     }
 
+    screen->dirty = true;
     return OK;
 }

src/vm_screen.c

@@ -61,6 +61,7 @@ vm_screen_create()
     screen->ycoords = 0;
     screen->last_key = '\0';
     screen->key_pressed = false;
+    screen->dirty = false;
 
     screen->window = NULL;
     screen->render = NULL;
@@ -209,6 +210,7 @@ vm_screen_active(vm_screen *screen)
         return true;
     }
 
+    SDL_Delay(2000);
     return false;
 }
 
@@ -220,6 +222,7 @@ void
 vm_screen_refresh(vm_screen *screen)
 {
     SDL_RenderPresent(screen->render);
+    screen->dirty = false;
 }
 
 /*
@@ -249,6 +252,7 @@ vm_screen_draw_rect(vm_screen *screen, vm_area *area)
     MAKE_SDL_RECT(rect, *area);
 
     SDL_RenderFillRect(screen->render, &rect);
+    screen->dirty = true;
 }
 
 /*
@@ -271,3 +275,9 @@ vm_screen_last_key(vm_screen *scr)
 {
     return scr->last_key;
 }
+
+bool
+vm_screen_dirty(vm_screen *scr)
+{
+    return scr->dirty;
+}