Prevent null pointer errors

Many functions which used the scr->nds pointer were not first checking
that the pointer was not null.

1 files changed, 40 insertions, 28 deletions

diff --git a/arm9/source/devices/screen.c b/arm9/source/devices/screen.c
index 5c16d8f..f1aa7f9 100644
--- a/arm9/source/devices/screen.c
+++ b/arm9/source/devices/screen.c
@@ -78,7 +78,9 @@ void set_palette_low(ScreenDevice *scr, u8 low) {
     u8 g = scr->palette_write >>  3 & 0x1e;
     u8 b = scr->palette_write <<  1 & 0x1e;
     scr->palette[i] = RGB15(r,g,b);
-    scr->nds->pal[i] = RGB15(r,g,b);
+    if (scr->nds) {
+        scr->nds->pal[i] = RGB15(r,g,b);
+    }
 }
 
 void push_sprite(SpriteBuffer *b, u8 row) {
@@ -145,47 +147,57 @@ void fill_layer(u16 *layer, u8 colour) {
 }
 
 void erase_screen(Screen *nds) {
-    dmaFillWords(0, nds->bg, TILES_MEM);
-    dmaFillWords(0, nds->fg, TILES_MEM);
+    if (nds) {
+        dmaFillWords(0, nds->bg, TILES_MEM);
+        dmaFillWords(0, nds->fg, TILES_MEM);
+    }
 };
 
 void flip_buffer(Screen *nds) {
-    dmaCopyWords(0, nds->bg, nds->bgv, TILES_MEM);
-    dmaCopyWords(0, nds->fg, nds->fgv, TILES_MEM);
-    for (int i=0; i<16; i++) {
-        nds->palv[i] = nds->pal[i];
+    if (nds) {
+        dmaCopyWords(0, nds->bg, nds->bgv, TILES_MEM);
+        dmaCopyWords(0, nds->fg, nds->fgv, TILES_MEM);
+        for (int i=0; i<16; i++) {
+            nds->palv[i] = nds->pal[i];
+        }
     }
 }
 
 void black_screen(Screen *nds) {
-    nds->pal[0] = RGB15(0,0,0);
-    dmaFillWords(0, nds->bgv, TILES_MEM);
-    dmaFillWords(0, nds->fgv, TILES_MEM);
+    if (nds) {
+        for (int i=0; i<16; i++) {
+            nds->palv[i] = RGB15(0,0,0);
+        }
+        dmaFillWords(0, nds->bgv, TILES_MEM);
+        dmaFillWords(0, nds->fgv, TILES_MEM);
+    }
 }
 // ---------------------------------------------------------------------------
 
 void draw_dispatch(ScreenDevice *scr, u8 draw) {
-    switch (draw >> 4) {
-    case 0x0:  scr_draw_pixel(scr, scr->nds->bg, draw); break;
-    case 0x1: scr_draw_sprite(scr, scr->nds->bg, draw); break;
-    case 0x2:  scr_fill_layer(scr, scr->nds->bg, draw); break;
-    case 0x3: scr_draw_sprite(scr, scr->nds->bg, draw); break;
-    case 0x4:   scr_draw_line(scr, scr->nds->bg, draw); break;
-    case 0x5:   scr_draw_line(scr, scr->nds->bg, draw); break;
-    case 0x6:   scr_draw_rect(scr, scr->nds->bg, draw); break;
-    case 0x7:   scr_draw_rect(scr, scr->nds->bg, draw); break;
-    case 0x8:  scr_draw_pixel(scr, scr->nds->fg, draw); break;
-    case 0x9: scr_draw_sprite(scr, scr->nds->fg, draw); break;
-    case 0xA:  scr_fill_layer(scr, scr->nds->fg, draw); break;
-    case 0xB: scr_draw_sprite(scr, scr->nds->fg, draw); break;
-    case 0xC:   scr_draw_line(scr, scr->nds->fg, draw); break;
-    case 0xD:   scr_draw_line(scr, scr->nds->fg, draw); break;
-    case 0xE:   scr_draw_rect(scr, scr->nds->fg, draw); break;
-    case 0xF:   scr_draw_rect(scr, scr->nds->fg, draw); break;
+    if (scr->nds) {
+        switch (draw >> 4) {
+        case 0x0:  scr_draw_pixel(scr, scr->nds->bg, draw); break;
+        case 0x1: scr_draw_sprite(scr, scr->nds->bg, draw); break;
+        case 0x2:  scr_fill_layer(scr, scr->nds->bg, draw); break;
+        case 0x3: scr_draw_sprite(scr, scr->nds->bg, draw); break;
+        case 0x4:   scr_draw_line(scr, scr->nds->bg, draw); break;
+        case 0x5:   scr_draw_line(scr, scr->nds->bg, draw); break;
+        case 0x6:   scr_draw_rect(scr, scr->nds->bg, draw); break;
+        case 0x7:   scr_draw_rect(scr, scr->nds->bg, draw); break;
+        case 0x8:  scr_draw_pixel(scr, scr->nds->fg, draw); break;
+        case 0x9: scr_draw_sprite(scr, scr->nds->fg, draw); break;
+        case 0xA:  scr_fill_layer(scr, scr->nds->fg, draw); break;
+        case 0xB: scr_draw_sprite(scr, scr->nds->fg, draw); break;
+        case 0xC:   scr_draw_line(scr, scr->nds->fg, draw); break;
+        case 0xD:   scr_draw_line(scr, scr->nds->fg, draw); break;
+        case 0xE:   scr_draw_rect(scr, scr->nds->fg, draw); break;
+        case 0xF:   scr_draw_rect(scr, scr->nds->fg, draw); break;
+        }
+        scr->dirty = true;
     }
     scr->px = scr->x;
     scr->py = scr->y;
-    scr->dirty = true;
 }
 
 void scr_draw_pixel(ScreenDevice *scr, u16 *layer, u8 draw) {