don't save to local storage unless edited; handle running out of local storage

presets/nes-conio/ex0.asm

@@ -0,0 +1,102 @@
+
+;;;;; CONSTANTS
+
+PPU_CTRL	equ $2000
+PPU_MASK	equ $2001
+PPU_STATUS	equ $2002
+PPU_SCROLL	equ $2005
+PPU_ADDR	equ $2006
+PPU_DATA	equ $2007
+DMC_FREQ	equ $4010
+
+;;;;; CARTRIDGE FILE HEADER
+
+	processor 6502
+	seg Header
+        org $7FF0
+
+NES_MAPPER	equ 0	;mapper number
+NES_PRG_BANKS	equ 2	;number of 16K PRG banks, change to 2 for NROM256
+NES_CHR_BANKS	equ 1	;number of 8K CHR banks (0 = RAM)
+NES_MIRRORING	equ 1	;0 horizontal, 1 vertical, 8 four screen
+
+	.byte $4e,$45,$53,$1a ; header
+	.byte NES_PRG_BANKS
+	.byte NES_CHR_BANKS
+	.byte NES_MIRRORING|(NES_MAPPER<<4)
+	.byte NES_MAPPER&$f0
+
+;;;;; CODE
+
+	seg Code
+	org $8000
+start:
+_exit:
+        sei			;disable IRQs
+        cld			;decimal mode not supported
+        ldx #$ff
+        txs			;set up stack pointer
+        inx			;increment X to 0
+        stx PPU_MASK		;disable rendering
+        stx DMC_FREQ		;disable DMC interrupts
+        stx PPU_CTRL		;disable NMI interrupts
+        jsr WaitSyncSafe	;wait for VSYNC
+; clear RAM -- not a subroutine because we clear the stack too
+	lda #0
+        tax
+.loop
+	sta $0,x
+	sta $100,x
+        ; skip $200-$2FF, used for OAM display list
+	sta $300,x
+	sta $400,x
+	sta $500,x
+	sta $600,x
+	sta $700,x
+        inx
+        bne .loop
+; wait for PPU warmup        
+        jsr WaitSync
+; set palette background
+        ldy #$0
+	lda #$3f
+	sta PPU_ADDR
+	sty PPU_ADDR
+        lda #$1c
+        sta PPU_DATA
+; enable PPU rendering
+        lda #0
+        sta PPU_ADDR
+        sta PPU_ADDR		;PPU addr = 0
+        sta PPU_SCROLL
+        sta PPU_SCROLL		;scroll = 0
+        lda #$90
+        sta PPU_CTRL		;enable NMI
+        lda #$1e
+        sta PPU_MASK		;enable rendering
+.endless
+	jmp .endless		;endless loop
+
+;;;;; SUBROUTINES
+
+; wait for VSYNC to start
+WaitSyncSafe: subroutine
+	bit PPU_STATUS
+WaitSync:
+	bit PPU_STATUS
+	bpl WaitSync
+        rts
+
+;;;;; INTERRUPT HANDLERS
+
+nmi:
+irq:
+	rti
+
+;;;;; CPU VECTORS
+
+	org $fffa
+       	.word nmi	;$fffa vblank nmi
+	.word start	;$fffc reset
+	.word irq	;$fffe irq / brk
+

presets/nes-conio/ex1.asm

@@ -4,16 +4,13 @@
 PPU_CTRL	equ $2000
 PPU_MASK	equ $2001
 PPU_STATUS	equ $2002
-PPU_OAM_ADDR	equ $2003
+OAM_ADDR	equ $2003
-PPU_OAM_DATA	equ $2004
+OAM_DATA	equ $2004
 PPU_SCROLL	equ $2005
 PPU_ADDR	equ $2006
 PPU_DATA	equ $2007
 PPU_OAM_DMA	equ $4014
-PPU_FRAMECNT	equ $4017
 DMC_FREQ	equ $4010
-CTRL_PORT1	equ $4016
-CTRL_PORT2	equ $4017
 
 ;;;;; ZERO-PAGE VARIABLES
 
@@ -45,16 +42,33 @@ NES_MIRRORING	equ 1	;0 horizontal, 1 vertical, 8 four screen
 	org $8000
 start:
 _exit:
-        sei
+        sei			;disable IRQs
+        cld			;decimal mode not supported
         ldx #$ff
-        txs
+        txs			;set up stack pointer
-        inx			;X=0
+        inx			;increment X to 0
         stx PPU_MASK		;disable rendering
-        stx DMC_FREQ		;disable DMC (samples)
+        stx DMC_FREQ		;disable DMC interrupts
-        stx PPU_CTRL		;disable NMI (interrupts)
+        stx PPU_CTRL		;disable NMI interrupts
-        jsr WaitSync		;wait for VSYNC
+        jsr WaitSyncSafe	;wait for VSYNC
+; clear RAM -- not a subroutine because we clear the stack too
+	lda #0
+        tax
+.loop
+	sta $0,x
+	sta $100,x
+        ; skip $200-$2FF, used for OAM display list
+	sta $300,x
+	sta $400,x
+	sta $500,x
+	sta $600,x
+	sta $700,x
+        inx
+        bne .loop
+; end of clear RAM routine
 	jsr SetPalette		;set colors
-        jsr ClearVRAM		;clear VRAM
+        jsr FillVRAM		;set PPU RAM
+        jsr WaitSync		;wait for VSYNC (and PPU warmup)
         lda #0
         sta PPU_ADDR
         sta PPU_ADDR		;PPU addr = 0
@@ -84,8 +98,8 @@ SetPalette: subroutine
 	bne .loop
         rts
 
-; clear video RAM
+; fill video RAM
-ClearVRAM: subroutine
+FillVRAM: subroutine
 	txa
 	ldy #$20
 	sty PPU_ADDR
@@ -101,11 +115,11 @@ ClearVRAM: subroutine
         rts
 
 ; wait for VSYNC to start
-WaitSync: subroutine
+WaitSyncSafe: subroutine
 	bit PPU_STATUS
-.1:
+WaitSync:
 	bit PPU_STATUS
-	bpl .1
+	bpl WaitSync
         rts
 
 ;;;;; INTERRUPT HANDLERS

src/platform/nes.js

@@ -8,10 +8,11 @@ var NES_NESLIB_PRESETS = [
 ];
 
 var NES_CONIO_PRESETS = [
-  {id:'hello.c', name:'Hello PPU'},
+  {id:'ex0.asm', name:'ASM: Initialization'},
-  {id:'conio.c', name:'Hello Console I/O'},
+  {id:'ex1.asm', name:'ASM: Scrolling Demo'},
-  {id:'siegegame.c', name:'Siege Game'},
+  {id:'hello.c', name:'C: Hello PPU'},
-  {id:'ex1.asm', name:'Assembly Example'},
+  {id:'conio.c', name:'C: Hello Console I/O'},
+  {id:'siegegame.c', name:'C: Siege Game'},
 ];
 
 /// JSNES

src/ui.js

@@ -35,13 +35,39 @@ Javatari.AUTO_START = false;
 var PRESETS; // presets array
 var platform_id;
 var platform; // platform object
+var originalFileID;
+var originalText;
 
 var toolbar = $("#controls_top");
 
+function getBiggestItems(storage) {
+  var items = [];
+  for (var i = 0; i < storage.length; i++) {
+    var key = storage.key(i);
+    items.push([lpad(storage.getItem(key).length+"", 12), key]);
+  }
+  items.sort();
+  var s = "";
+  for (var i=items.length-5; i<items.length; i++) {
+    s += items[i] + "\n";
+  }
+  return s;
+}
+
 var FileStore = function(storage, prefix) {
   var self = this;
   this.saveFile = function(name, text) {
+    try {
       storage.setItem(prefix + name, text);
+    } catch (e) {
+      if (e.name == 'NS_ERROR_DOM_QUOTA_REACHED') {
+        console.log(e);
+        alert("Sorry, you've reached your local storage quota for this browser.\n\nHere are the biggest items:\n\n" +
+          getBiggestItems(storage));
+      } else {
+        throw e;
+      }
+    }
   }
   this.loadFile = function(name) {
     return storage.getItem(prefix + name) || storage.getItem(name);
@@ -181,7 +207,7 @@ function setLastPreset(id) {
 }
 
 function updatePreset(current_preset_id, text) {
-  if (text.trim().length) {
+  if (text.trim().length && (originalFileID != current_preset_id || text != originalText)) {
     store.saveFile(current_preset_id, text);
   }
 }
@@ -193,6 +219,8 @@ function loadCode(text, fileid) {
   editor.clearHistory();
   current_output = null;
   setLastPreset(fileid);
+  originalFileID = fileid;
+  originalText = text;
 }
 
 function loadFile(fileid, filename, index) {
@@ -220,7 +248,6 @@ function loadFile(fileid, filename, index) {
     var ext = platform.getToolForFilename(fileid);
     $.get( "presets/"+platform_id+"/skeleton."+ext, function( text ) {
       loadCode(text, fileid);
-      updatePreset(fileid, text);
     }, 'text')
     .fail(function() {
       alert("Could not load skeleton for " + platform_id + "/" + ext);