From 616bfdcc58b9672cd14b3455cb0edeefd8125a53 Mon Sep 17 00:00:00 2001
From: Peter Evans <peter@modul8r.com>
Date: Wed, 4 Apr 2018 22:01:46 -0500
Subject: [PATCH] Implement rect change stack

---
 src/vm_screen.c | 59 ++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 53 insertions(+), 6 deletions(-)

diff --git a/src/vm_screen.c b/src/vm_screen.c
index 46567ee..568a692 100644
--- a/src/vm_screen.c
+++ b/src/vm_screen.c
@@ -15,6 +15,28 @@
 #include "vm_event.h"
 #include "vm_screen.h"
 
+typedef struct {
+    /*
+     * The point coordinates of the change on-screen that we are looking
+     * to make
+     */
+    vm_area area;
+
+    /*
+     * The new color of the pixel
+     */
+    vm_color clr;
+} change;
+
+/*
+ * An array of changes, arranged in a stack, plus the position in the
+ * stack where we currently are at.
+ */
+static change changestack[65536];
+static int changepos = 0;
+
+static vm_color curcolor;
+
 struct timeval refresh_time;
 
 /*
@@ -205,7 +227,7 @@ vm_screen_active(vm_screen *scr)
 void
 vm_screen_prepare(vm_screen *scr)
 {
-    //SDL_RenderClear(scr->render);
+    SDL_RenderClear(scr->render);
 }
 
 /*
@@ -213,10 +235,22 @@ vm_screen_prepare(vm_screen *scr)
  * made recently.
  */
 void
-vm_screen_refresh(vm_screen *screen)
+vm_screen_refresh(vm_screen *scr)
 {
-    SDL_RenderPresent(screen->render);
-    screen->dirty = false;
+    change *chg;
+
+    while (changepos >= 0) {
+        chg = &changestack[changepos--];
+
+        SDL_SetRenderDrawColor(scr->render, chg->clr.r, chg->clr.g, 
+                               chg->clr.b, SDL_ALPHA_OPAQUE);
+
+        MAKE_SDL_RECT(rect, chg->area);
+        SDL_RenderFillRect(scr->render, &rect);
+    }
+
+    SDL_RenderPresent(scr->render);
+    scr->dirty = false;
 }
 
 /*
@@ -229,6 +263,8 @@ vm_screen_set_color(vm_screen *scr, vm_color clr)
         SDL_SetRenderDrawColor(scr->render, clr.r, clr.g, clr.b,
                                SDL_ALPHA_OPAQUE);
     }
+
+    curcolor = clr;
 }
 
 /*
@@ -238,11 +274,22 @@ vm_screen_set_color(vm_screen *scr, vm_color clr)
 void
 vm_screen_draw_rect(vm_screen *screen, vm_area *area)
 {
+    change *chg;
+
+    // FIXME: magic number
+    if (changepos >= 65536) {
+        return;
+    }
+
+    chg = &changestack[changepos++];
+    memcpy(&chg->area, area, sizeof(vm_area));
+    chg->clr = curcolor;
+
     // The renderer will take care of translating the positions and
     // sizes into whatever the window is really at.
-    MAKE_SDL_RECT(rect, *area);
+    //MAKE_SDL_RECT(rect, *area);
 
-    SDL_RenderFillRect(screen->render, &rect);
+    //SDL_RenderFillRect(screen->render, &rect);
     screen->dirty = true;
 }