gpu: expose the rendering implementation

The rendering implementation is needed for using Gio UI with external
window libraries such as GLFW. Expose it in the new package gpu.

Updates #26

Signed-off-by: Elias Naur <mail@eliasnaur.com>

app/headless/headless.go

@@ -9,8 +9,8 @@ import (
 	"image"
 	"runtime"
 
-	"gioui.org/app/internal/gl"
-	"gioui.org/app/internal/gpu"
+	"gioui.org/gpu"
+	"gioui.org/gpu/gl"
 	"gioui.org/op"
 )
 

app/headless/headless_darwin.go

@@ -2,8 +2,10 @@
 
 package headless
 
-import "gioui.org/app/internal/gl"
-import "gioui.org/app/internal/gl/impl"
+import (
+	"gioui.org/app/internal/glimpl"
+	"gioui.org/gpu/gl"
+)
 
 /*
 #cgo CFLAGS: -DGL_SILENCE_DEPRECATION -Werror -Wno-deprecated-declarations -fmodules -fobjc-arc -x objective-c
@@ -21,7 +23,7 @@ type nsContext struct {
 
 func newContext() (context, error) {
 	ctx := C.gio_headless_newContext()
-	return &nsContext{ctx: ctx, c: new(impl.Functions)}, nil
+	return &nsContext{ctx: ctx, c: new(glimpl.Functions)}, nil
 }
 
 func (c *nsContext) MakeCurrent() error {

app/headless/headless_js.go

@@ -6,8 +6,8 @@ import (
 	"errors"
 	"syscall/js"
 
-	"gioui.org/app/internal/gl"
-	"gioui.org/app/internal/gl/impl"
+	"gioui.org/gpu/gl"
+	"gioui.org/app/internal/glimpl"
 )
 
 type jsContext struct {
@@ -27,7 +27,7 @@ func newContext() (*jsContext, error) {
 	if ctx.IsNull() {
 		return nil, errors.New("headless: webgl is not supported")
 	}
-	f := &impl.Functions{Ctx: ctx}
+	f := &glimpl.Functions{Ctx: ctx}
 	if err := f.Init(version); err != nil {
 		return nil, err
 	}