Completely separate backends from platform implementation

This removes PuglContextType and allows the user to pass a backend directly.
Normally this would come from one of the two accessors declared in the headers,
but it would be possible to add backends without changing any of the existing
code at all.

Unfortunately, it is not possible to preserve backwards compatibility and
achieve the ultimate goal of linking only to the required dependencies, so
puglInitContextType() has just been removed.

12 files changed, 47 insertions, 76 deletions

diff --git a/pugl/pugl.h b/pugl/pugl.h
index b88392b..7e6036f 100644
--- a/pugl/pugl.h
+++ b/pugl/pugl.h
@@ -94,14 +94,6 @@ typedef enum {
 } PuglStatus;
 
 /**
-   Drawing context type.
-*/
-typedef enum {
-	PUGL_GL    = 1 << 0,  /**< OpenGL (3D) */
-	PUGL_CAIRO = 1 << 1   /**< Cairo (2D) */
-} PuglContextType;
-
-/**
    Window hint.
 */
 typedef enum {
@@ -503,10 +495,15 @@ PUGL_API void
 puglInitTransientFor(PuglView* view, uintptr_t parent);
 
 /**
-   Set the context type before creating a window.
+   Set the graphics backend to use.
+
+   This needs to be called once before creating the window to set the graphics
+   backend.  There are two backend accessors included with pugl:
+   puglGlBackend() and puglCairoBackend(), declared in pugl_gl_backend.h and
+   pugl_cairo_backend.h, respectively.
 */
-PUGL_API void
-puglInitContextType(PuglView* view, PuglContextType type);
+PUGL_API int
+puglInitBackend(PuglView* view, const PuglBackend* backend);
 
 /**
    @}
@@ -581,8 +578,10 @@ puglGetSize(PuglView* view, int* width, int* height);
 /**
    Get the drawing context.
 
-   For PUGL_GL contexts, this is unused and returns NULL.
-   For PUGL_CAIRO contexts, this returns a pointer to a cairo_t.
+   The context is only guaranteed to be available during an expose.
+
+   For OpenGL backends, this is unused and returns NULL.
+   For Cairo backends, this returns a pointer to a `cairo_t`.
 */
 PUGL_API void*
 puglGetContext(PuglView* view);
diff --git a/pugl/pugl.hpp b/pugl/pugl.hpp
index 0646d28..d2702ab 100644
--- a/pugl/pugl.hpp
+++ b/pugl/pugl.hpp
@@ -66,8 +66,8 @@ public:
 		puglInitTransientFor(_view, parent);
 	}
 
-	virtual void initContextType(PuglContextType type) {
-		puglInitContextType(_view, type);
+	virtual void initBackend(const PuglBackend* backend) {
+		puglInitBackend(_view, backend);
 	}
 
 	virtual void createWindow(const char* title) {
diff --git a/pugl/pugl_cairo_backend.h b/pugl/pugl_cairo_backend.h
index b48915e..3330c08 100644
--- a/pugl/pugl_cairo_backend.h
+++ b/pugl/pugl_cairo_backend.h
@@ -14,15 +14,24 @@
   OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
 
+/**
+   @file pugl_cairo_backend.h Declaration of Cairo backend accessor.
+*/
+
 #ifndef PUGL_CAIRO_BACKEND_H
 #define PUGL_CAIRO_BACKEND_H
 
-#include "pugl/pugl_internal_types.h"
+#include "pugl/pugl.h"
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+/**
+   Cairo graphics backend accessor.
+
+   Pass the return value to puglInitBackend() to draw to a view with Cairo.
+*/
 PUGL_API const PuglBackend*
 puglCairoBackend(void);
 
diff --git a/pugl/pugl_gl_backend.h b/pugl/pugl_gl_backend.h
index 11f4e4b..5913b95 100644
--- a/pugl/pugl_gl_backend.h
+++ b/pugl/pugl_gl_backend.h
@@ -14,15 +14,24 @@
   OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
 
+/**
+   @file pugl_gl_backend.h Declaration of OpenGL backend accessor.
+*/
+
 #ifndef PUGL_GL_BACKEND_H
 #define PUGL_GL_BACKEND_H
 
-#include "pugl/pugl_internal_types.h"
+#include "pugl/pugl.h"
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+/**
+   OpenGL graphics backend.
+
+   Pass the return value to puglInitBackend() to draw to a view with OpenGL.
+*/
 PUGL_API const PuglBackend*
 puglGlBackend(void);
 
diff --git a/pugl/pugl_internal.h b/pugl/pugl_internal.h
index 312329d..1f4cd4d 100644
--- a/pugl/pugl_internal.h
+++ b/pugl/pugl_internal.h
@@ -17,15 +17,9 @@
 /**
    @file pugl_internal.h Private platform-independent definitions.
 
-   Note this file contains function definitions, so it must be compiled into
-   the final binary exactly once.  Each platform specific implementation file
-   including it once should achieve this.
-
-   If you are copying the pugl code into your source tree, the following
-   symbols can be defined to tweak pugl behaviour:
-
-   PUGL_HAVE_CAIRO: Include Cairo support code.
-   PUGL_HAVE_GL:    Include OpenGL support code.
+   Note that this file contains function definitions, so it must be compiled
+   into the final binary exactly once.  Each platform specific implementation
+   file including it once should achieve this.
 */
 
 #include "pugl/pugl.h"
@@ -59,7 +53,6 @@ puglInit(int* PUGL_UNUSED(pargc), char** PUGL_UNUSED(argv))
 	}
 
 	view->hints      = puglDefaultHints();
-	view->ctx_type   = PUGL_GL;
 	view->impl       = impl;
 	view->width      = 640;
 	view->height     = 480;
@@ -166,10 +159,11 @@ puglInitTransientFor(PuglView* view, uintptr_t parent)
 	view->transient_parent = parent;
 }
 
-void
-puglInitContextType(PuglView* view, PuglContextType type)
+int
+puglInitBackend(PuglView* view, const PuglBackend* backend)
 {
-	view->ctx_type = type;
+	view->backend = backend;
+	return 0;
 }
 
 void
diff --git a/pugl/pugl_internal_types.h b/pugl/pugl_internal_types.h
index 5f81f97..9a0bedc 100644
--- a/pugl/pugl_internal_types.h
+++ b/pugl/pugl_internal_types.h
@@ -63,7 +63,6 @@ struct PuglViewImpl {
 	PuglNativeWindow   parent;
 	double             start_time;
 	uintptr_t          transient_parent;
-	PuglContextType    ctx_type;
 	PuglHints          hints;
 	int                width;
 	int                height;
diff --git a/pugl/pugl_osx.m b/pugl/pugl_osx.m
index 30eb84d..6ddb24d 100644
--- a/pugl/pugl_osx.m
+++ b/pugl/pugl_osx.m
@@ -745,13 +745,6 @@ puglCreateWindow(PuglView* view, const char* title)
 	[NSAutoreleasePool new];
 	impl->app = [NSApplication sharedApplication];
 
-	view->backend = puglGlBackend();
-	if (view->ctx_type == PUGL_CAIRO) {
-#ifdef PUGL_HAVE_CAIRO
-		view->backend = puglCairoBackend();
-#endif
-	}
-
 	impl->glview               = [PuglOpenGLView alloc];
 	impl->glview->trackingArea = nil;
 	impl->glview->markedText   = [[NSMutableAttributedString alloc] init];
diff --git a/pugl/pugl_win.c b/pugl/pugl_win.c
index 799850e..b34ca43 100644
--- a/pugl/pugl_win.c
+++ b/pugl/pugl_win.c
@@ -21,13 +21,6 @@
 #include "pugl/pugl_internal.h"
 #include "pugl/pugl_win.h"
 
-#ifdef PUGL_HAVE_GL
-#include "pugl/pugl_gl_backend.h"
-#endif
-#ifdef PUGL_HAVE_CAIRO
-#include "pugl/pugl_cairo_backend.h"
-#endif
-
 #include <windows.h>
 #include <windowsx.h>
 
@@ -91,17 +84,6 @@ puglCreateWindow(PuglView* view, const char* title)
 
 	title = title ? title : "Window";
 
-	if (view->ctx_type == PUGL_GL) {
-#ifdef PUGL_HAVE_GL
-		view->backend = puglGlBackend();
-#endif
-	}
-	if (view->ctx_type == PUGL_CAIRO) {
-#ifdef PUGL_HAVE_CAIRO
-		view->backend = puglCairoBackend();
-#endif
-	}
-
 	// Get refresh rate for resize draw timer
 	DEVMODEA devMode = {0};
 	EnumDisplaySettingsA(NULL, ENUM_CURRENT_SETTINGS, &devMode);
diff --git a/pugl/pugl_x11.c b/pugl/pugl_x11.c
index d9620e1..ad9acc8 100644
--- a/pugl/pugl_x11.c
+++ b/pugl/pugl_x11.c
@@ -25,13 +25,6 @@
 #include "pugl/pugl_internal.h"
 #include "pugl/pugl_x11.h"
 
-#ifdef PUGL_HAVE_GL
-#include "pugl/pugl_gl_backend.h"
-#endif
-#ifdef PUGL_HAVE_CAIRO
-#include "pugl/pugl_cairo_backend.h"
-#endif
-
 #include <X11/Xatom.h>
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
@@ -83,17 +76,6 @@ puglCreateWindow(PuglView* view, const char* title)
 	impl->atoms.NET_WM_STATE_DEMANDS_ATTENTION =
 		XInternAtom(display, "_NET_WM_STATE_DEMANDS_ATTENTION", 0);
 
-	if (view->ctx_type == PUGL_GL) {
-#ifdef PUGL_HAVE_GL
-		view->backend = puglGlBackend();
-#endif
-	}
-	if (view->ctx_type == PUGL_CAIRO) {
-#ifdef PUGL_HAVE_CAIRO
-		view->backend = puglCairoBackend();
-#endif
-	}
-
 	if (!view->backend || !view->backend->configure) {
 		return 1;
 	} else if (view->backend->configure(view) || !impl->vi) {
diff --git a/pugl/pugl_x11_cairo.c b/pugl/pugl_x11_cairo.c
index c52b875..1a75b1c 100644
--- a/pugl/pugl_x11_cairo.c
+++ b/pugl/pugl_x11_cairo.c
@@ -118,7 +118,8 @@ puglX11CairoGetContext(PuglView* view)
 	return surface->cr;
 }
 
-const PuglBackend* puglCairoBackend(void)
+const PuglBackend*
+puglCairoBackend(void)
 {
 	static const PuglBackend backend = {
 		puglX11CairoConfigure,
diff --git a/test/pugl_cairo_test.c b/test/pugl_cairo_test.c
index ba1dad3..57f27ec 100644
--- a/test/pugl_cairo_test.c
+++ b/test/pugl_cairo_test.c
@@ -19,6 +19,7 @@
 */
 
 #include "pugl/pugl.h"
+#include "pugl/pugl_cairo_backend.h"
 
 #include <cairo.h>
 
@@ -185,7 +186,7 @@ main(int argc, char** argv)
 	puglInitWindowSize(view, 512, 512);
 	puglInitWindowMinSize(view, 256, 256);
 	puglInitWindowHint(view, PUGL_RESIZABLE, resizable);
-	puglInitContextType(view, PUGL_CAIRO);
+	puglInitBackend(view, puglCairoBackend());
 
 	puglIgnoreKeyRepeat(view, ignoreKeyRepeat);
 	puglSetEventFunc(view, onEvent);
diff --git a/test/pugl_test.c b/test/pugl_test.c
index dfc06c6..b83263f 100644
--- a/test/pugl_test.c
+++ b/test/pugl_test.c
@@ -24,6 +24,7 @@
 
 #include "pugl/gl.h"
 #include "pugl/pugl.h"
+#include "pugl/pugl_gl_backend.h"
 
 #include <locale.h>
 #include <math.h>
@@ -171,6 +172,7 @@ main(int argc, char** argv)
 	puglInitWindowSize(view, 512, 512);
 	puglInitWindowMinSize(view, 256, 256);
 	puglInitWindowAspectRatio(view, 1, 1, 16, 9);
+	puglInitBackend(view, puglGlBackend());
 
 	puglInitWindowHint(view, PUGL_RESIZABLE, resizable);
 	puglInitWindowHint(view, PUGL_SAMPLES, samples);