Very minimal OSX platform layer experiments

David Butler

#12152

June 7, 2017

Not sure if I want to make a full blown project out of it, but I at-least wanted to share my current progress.

Over the weekend I was playing around with trying to make a minimal OSX platform layer. Im trying to avoid all the latency and overhead that the objective C runtime adds... This is what I got so far, its pretty quick, but it uses some "hidden" apis, so there might be some stability implications of doing it this way, but I'm thinking its probably not that big of a deal... Anyway here is some code:

/*

mkdir -p build/test.app/Contents/MacOS
clang++ --std=c++11 
 -fno-exceptions
 -fno-rtti
 -mmacosx-version-min=10.9
 -Wno-writable-strings
 -Wno-deprecated-declarations
 -framework OpenGL
 -framework Carbon
 -g gui8.cpp
 -o build/test.app/Contents/MacOS/test

  
 */


#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>

#include <ApplicationServices/ApplicationServices.h>
#include <Carbon/Carbon.h>
#include <OpenGL/CGLTypes.h>
#include <OpenGL/CGLCurrent.h>
#include <OpenGL/OpenGL.h>
#include <OpenGL/gl.h>

typedef int CGSConnectionID;
typedef int CGSWindowID;
typedef int CGSSurfaceID;

typedef uint32_t _CGWindowID;

extern "C" {

typedef int CGSConnection;
typedef int CGSWindow;
typedef int CGSValue;

extern CGSValue CGSCreateCStringNoCopy(const char str);
extern char CGSCStringValue(CGSValue string);
extern int CGSIntegerValue(CGSValue intVal);

typedef enum _CGSWindowOrderingMode {
   kCGSOrderAbove                =  1, // Window is ordered above target.
   kCGSOrderBelow                = -1, // Window is ordered below target.
   kCGSOrderOut                  =  0  // Window is removed from the on-screen window list.
} CGSWindowOrderingMode;

typedef void *CGSRegion;
typedef CGSRegion *CGSRegionRef;
typedef CGSWindow *CGSWindowRef;

extern CGError CGSNewWindow( CGSConnection cid, int, float, float, const CGSRegion, CGSWindowRef);
extern CGError CGSNewRegionWithRect( const CGRect * rect, CGSRegionRef newRegion );
extern OSStatus CGSOrderWindow(CGSConnection cid, CGSWindow win, CGSWindowOrderingMode place, CGSWindow relativeToWindow /* nullable */);
extern OSStatus CGSSetWindowProperty(const CGSConnection cid, CGSWindow wid, CGSValue key, CGSValue value);
extern CGSConnectionID CGSMainConnectionID(void);
extern CGError CGSAddSurface(CGSConnectionID cid, _CGWindowID wid, CGSSurfaceID *sid);
extern CGError CGSSetSurfaceBounds(CGSConnectionID cid, _CGWindowID wid, CGSSurfaceID sid, CGRect rect);
extern CGError CGSOrderSurface(CGSConnectionID cid, _CGWindowID wid, CGSSurfaceID sid, int a, int b);
extern OSStatus CGSMoveWindow(const CGSConnection cid, const CGSWindow wid, CGPoint *point);
extern CGLError CGLSetSurface(CGLContextObj gl, CGSConnectionID cid, CGSWindowID wid, CGSSurfaceID sid);
extern Boolean ConvertEventRefToEventRecord(EventRef       inEvent, EventRecord *  outEvent);

}
#define kCGSBufferedBackingType 2


int main () {

    CGLContextObj cgl_context = NULL;
    CGSWindow window = 0;

    int width = 500, height = 500;
    CGPoint window_pos = { .x = 200, .y = 200 };
    bool mouse_is_down = false;
    bool quit = false;

    CGSConnectionID connection_id = CGSMainConnectionID();
    assert(connection_id);

    {

        CGSRegion region = NULL;
        CGRect r = CGRectMake(0,0, width, height);
        auto err1 = CGSNewRegionWithRect(&r, &region);
        assert(region);
        auto err2 = CGSNewWindow(connection_id, kCGSBufferedBackingType, window_pos.x, window_pos.y, region, &window);
        assert(window);
        auto err3 = CGSOrderWindow(connection_id, window, kCGSOrderAbove, 0);
        assert (err3 == kCGErrorSuccess);


        CGLPixelFormatAttribute attributes[] = {
            kCGLPFADoubleBuffer,
            kCGLPFAAccelerated, // Hardware rendering
            // kCGLPFARendererID, (CGLPixelFormatAttribute) kCGLRendererGenericFloatID, // Software rendering
            (CGLPixelFormatAttribute)0
        };

        CGLPixelFormatObj pix;
        GLint num;
        auto err4 = CGLChoosePixelFormat(attributes, &pix, &num);
        assert(err4 == kCGLNoError); // CGLErrorString(err1)
        assert(pix);

        CGLCreateContext(pix, NULL, &cgl_context);
        assert(cgl_context);
        CGLDestroyPixelFormat(pix);
        CGLSetCurrentContext(cgl_context);

        GLint v_sync_enabled = 1;
        CGLSetParameter(cgl_context, kCGLCPSwapInterval, &v_sync_enabled);

        CGSSurfaceID surface_id = 0;
        auto err5 = CGSAddSurface(connection_id, window, &surface_id);
        assert(err5 == kCGErrorSuccess);
        auto err6 = CGSSetSurfaceBounds(connection_id, window, surface_id, CGRectMake(0, 0, width, height));
        assert(err6 == kCGErrorSuccess);
        auto err7 = CGSOrderSurface(connection_id, window, surface_id, 1, 0);
        assert(err7 == kCGErrorSuccess);
 
        auto err8 = CGLSetSurface(cgl_context, connection_id, window, surface_id);
        assert(err8 == kCGLNoError);
 
        GLint drawable = 0;
        CGLGetParameter(cgl_context, kCGLCPHasDrawable, &drawable);
        assert(drawable == 1);



        
    }

    assert(glGetError() == GL_NO_ERROR);
    
    CGPoint drag_starting_position;
    bool drag_started = false;
    while (!quit) {

        {
            EventTargetRef event_target = GetEventDispatcherTarget(); // No clue what the point of this is
    
            EventRef carbon_event_ref;
            while (ReceiveNextEvent(0, NULL, kEventDurationNoWait ,true, &carbon_event_ref)== noErr) {
                
                if (auto cg_event = CopyEventCGEvent(carbon_event_ref)) {

                    char* event_type_string = NULL;
                    auto cg_event_type = CGEventGetType(cg_event);
                    switch (cg_event_type) {


                        case kCGEventLeftMouseDown: {
                            event_type_string = "kCGEventLeftMouseDown";
                    
                            auto err3 = CGSOrderWindow(connection_id, window, kCGSOrderAbove, 0);
                            assert (err3 == kCGErrorSuccess);

                            mouse_is_down = true;


                        } break;
                        case kCGEventLeftMouseUp: {
                            event_type_string = "kCGEventLeftMouseUp";
                            mouse_is_down = false;
                            drag_started = false;
                        } break;
                        case kCGEventRightMouseDown: { event_type_string = "kCGEventRightMouseDown"; quit=true; } break;
                        case kCGEventRightMouseUp: { event_type_string = "kCGEventRightMouseUp"; } break;
                        case kCGEventMouseMoved: {
                            event_type_string = "kCGEventMouseMoved";
                        } break;
                        case kCGEventLeftMouseDragged: {
                            event_type_string = "kCGEventLeftMouseDragged";

                            if (!drag_started) {
                                drag_started = true;
                                drag_starting_position = CGEventGetLocation(cg_event);
                            }
                    
                            CGPoint mouse_pos = CGEventGetLocation(cg_event);
                            window_pos.x = window_pos.x + mouse_pos.x - drag_starting_position.x;
                            window_pos.y = window_pos.y + mouse_pos.y - drag_starting_position.y;
                            drag_starting_position = CGEventGetLocation(cg_event);
                                
                            auto err = CGSMoveWindow(connection_id, window, &window_pos);
                    
                        } break;
                        case kCGEventRightMouseDragged: { event_type_string = "kCGEventRightMouseDragged"; } break;
                        case kCGEventKeyDown: { event_type_string = "kCGEventKeyDown"; } break;
                        case kCGEventKeyUp: { event_type_string = "kCGEventKeyUp"; } break;
                        case kCGEventFlagsChanged: { event_type_string = "kCGEventFlagsChanged"; } break;
                        case kCGEventScrollWheel: { event_type_string = "kCGEventScrollWheel"; } break;
                        case kCGEventTabletPointer: { event_type_string = "kCGEventTabletPointer"; } break;
                        case kCGEventTabletProximity: { event_type_string = "kCGEventTabletProximity"; } break;
                        case kCGEventOtherMouseDown: { event_type_string = "kCGEventOtherMouseDown"; } break;
                        case kCGEventOtherMouseUp: { event_type_string = "kCGEventOtherMouseUp"; } break;
                        case kCGEventOtherMouseDragged: { event_type_string = "kCGEventOtherMouseDragged"; } break;
                        case kCGEventTapDisabledByTimeout: { event_type_string = "kCGEventTapDisabledByTimeout"; } break;
                        case kCGEventTapDisabledByUserInput: { event_type_string = "kCGEventTapDisabledByUserInput"; } break;
                        default: { event_type_string = "UNKNOWN"; } break;
                    }
            
                    printf("CG:Y %llu %s:%d ", CGEventGetTimestamp(cg_event), event_type_string, cg_event_type);
                    CFRelease(cg_event);
                } else {
                    printf("CG:N ");
                }

                char* what_str = NULL;
                EventRecord carbon_event;
                if (bool conv = ConvertEventRefToEventRecord(carbon_event_ref, &carbon_event)) {

                    switch (carbon_event.what) {
                        case nullEvent: what_str = "nullEvent"; break;
                        case mouseDown: what_str = "mouseDown"; break;
                        case mouseUp: what_str = "mouseUp"; break;
                        case keyDown: what_str = "keyDown"; break;
                        case autoKey: what_str = "autoKey"; break;
                        case updateEvt: what_str = "updateEvt"; break;
                        case diskEvt: what_str = "diskEvt"; break;
                        case activateEvt: what_str = "activateEvt"; break;
                        case osEvt: what_str = "osEvt"; break;
                        case kHighLevelEvent: what_str = "kHighLevelEvent"; break;
                        default: what_str = "UNKNOWN"; break;
                    };

        
                    printf("evt: %u %s:%hu", carbon_event.when, what_str, carbon_event.what);
                    if(conv && (carbon_event.what == kHighLevelEvent))
                        AEProcessAppleEvent(&carbon_event);
                }
	
                SendEventToEventTarget (carbon_event_ref, event_target);
                ReleaseEvent(carbon_event_ref);
                printf("\n");
            }
        }
        
        glClearColor(mouse_is_down?1:0,1,0,1);
        glClear(GL_COLOR_BUFFER_BIT);
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
        static float a = 0;
        glRotatef(a * 1000, 0, 0, 1);
        // printf("a: %f\n", a);
        a= a + .001;
        glBegin(GL_QUADS);
        if (a>1.5) a=0;
        glColor4f(0,a,1,1);
        glVertex2f(0.25, 0.25);
        glVertex2f(0.75, 0.25);
        glVertex2f(0.75, 0.75);
        glVertex2f(0.25, 0.75);
        glEnd();

        auto err1 = CGLFlushDrawable(cgl_context);
        assert(err1 == kCGLNoError);

        assert(glGetError() == GL_NO_ERROR);

    }
    
    CGLSetCurrentContext(NULL);
    CGLDestroyContext(cgl_context);

}

There is still a bit more needed in order to be a well behaved OS X app...

Edited by Jeroen van Rijn on June 8, 2017, 9:24pm Reason: &region;

Mārtiņš Možeiko

#12153

June 7, 2017

Croepha
it uses some "hidden" apis, so there might be some stability implications of doing it this way, but I'm thinking its probably not that big of a deal...

This is all fine for quick hacks, experimenting or just having fun. But I would recommend avoiding shipping app that uses undocumented and private CoreGraphics APIs. You'll never know when your app will stop working in future because of this (new OSX update, new sandbox restrictions, private API will change parameters/names/structs, etc..)

Edited by Mārtiņš Možeiko on June 7, 2017, 7:06pm

David Butler

#12154

June 7, 2017

I have actually considered that a bunch, and you are probably right and it would break at some point. but this code should work as far back as 10.5 probably even to 10.3 (haven't tested it) with some tweaking so I'm thinking that its probably not likely to happen very often. Even some so-called "stable" APIs don't last that long... I know that other applications in the wild do use these hidden APIs so if the APIs change then more things would break then just this code....

In my opinion, I think the payoffs are worth the risk... For certain products

So, if one were to ship something like this, I would probably recommend that you would do it in such a way that you could always failover to a better supported Cocoa platform layer.

Edited by David Butler on June 7, 2017, 7:36pm

Matt Hartley

#12160

June 8, 2017

That's really nice! I've tried to use CoreGraphics before but I couldn't find enough info about it.

I really hate Objective-C and Cocoa, so I gave up on that and I just use SDL on OSX now.

Nice job getting that working.