More Area planning.

areaplan.md

@@ -1,5 +1,4 @@
 ```go
-```go
 type Area struct {		// implements Control
 	// Paint receives requests to redraw from the window system.
 	Paint		chan PaintRequest
@@ -42,6 +41,8 @@ func myAreaGoroutine(area *ui.Area, start <-chan bool) {
 }
 ```
 
+TODO is there a race on `area.SetSize()`?
+
 ## Windows
 TODO
 
@@ -79,4 +80,67 @@ func draw_callback(widget *C.GtkWidget, cr *C.cairo_t, data C.gpointer) C.gboole
 TODO figure out how scrolling plays into this
 
 ## Cocoa
-TODO
+For this one we **must** create a subclass of `NSView` that overrides the drawing and keyboard/mouse event messages.
+
+The drawing message is `-[NSView drawRect:]`, which just takes the `NSRect` as an argument. So we already need to use `bleh_darwin.m` to grab the actual `NSRect` and convert it into something with a predictable data type before passing it back to Go. If we do this:
+```go
+//export our_drawRect
+func our_drawRect(self C.id, rect C.struct_xrect) {
+```
+we can call `our_drawRect()` from this C wrapper:
+```objective-c
+extern void our_drawRect(id, struct xrect);
+
+void _our_drawRect(id self, SEL sel, NSRect r)
+{
+	struct xrect t;
+
+	t.x = (int64_t) s.origin.x;
+	t.y = (int64_t) s.origin.y;
+	t.width = (int64_t) s.size.width;
+	t.height = (int64_t) s.size.height;
+	our_drawRect(self, t);
+}
+```
+This just leaves `our_drawRect` itself. For this mockup, I will use "Objective-Go":
+```go
+//export our_drawRect
+func our_drawRect(self C.id, rect C.struct_xrect) {
+	s := getSysData(self)
+	cliprect := image.Rect(int(rect.x), int(rect.y), int(rect.width), int(rect.height))
+	imgret := make(chan *image.NRGBA)
+	defer close(imgret)
+	s.paint <- PaintRequest{
+		Rect:		cliprect,
+		Out:		imgret,
+	}
+	i := <-imgret
+	// the NSBitmapImageRep constructor requires a list of pointers
+	_bitmapData := [1]*uint8{&i.Pix[0]}
+	bitmapData := (**C.uchar)(unsafe.Pointer(&bitmapData))
+	bitmap := [[NSBitmapImageRep alloc]
+		initWithBitmapDataPlanes:bitmapData
+		pixelsWide:i.Rect.Dx()
+		pixelsHigh:i.Rect.Dy()
+		bitsPerSample:8
+		samplesPerPixel:4
+		hasAlpha:YES
+		isPlanar:NO
+		colorSpaceName:NSCalibratedRGBColorSpace		// TODO NSDeviceRGBColorSpace?
+		bytesPerRow:i.Stride
+		bitsPerPixel:32]
+	[bitmap drawAtPoint:NSMakePoint(cliprect.x, cliprect.y)]
+	[bitmap release]
+}
+```
+Due to the utter complexity of all that `NSImage` stuff, I might just have another C function that performs the `NSBitmapImageRep` constructor using the `image.NRGBA` fields.
+
+Finally, we need to override `-[NSView isFlipped]` since we want to keep (0,0) at the top-left:
+```go
+//export our_isFlipped
+func our_isFlipped(self C.id, sel C.SEL) C.BOOL {
+	return C.BOOL(C.YES)
+}
+```
+
+TODO figure out scrolling