mainloop: add optional C implementation

This uses a specific build tag so as not to be on by default.
bonki · May 24, 2019 · bb1f0be · bb1f0be
1 parent 799a307
commit bb1f0be
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Showing 4 changed files with 109 additions and 28 deletions.
diff --git a/README.mdown b/README.mdown
@@ -135,3 +135,12 @@ somewhere in your program. If you don't have `gcc` installed and on your `PATH`,
 you can alternatively add `-linkmode internal` to the `-ldflags` of your `go build` command like so:
 
     go build -ldflags="-H windowsgui -linkmode internal"
+
+CGo Optimizations
+=================
+
+The usual default message loop includes calls to win32 API functions, which incurs a decent amount
+of runtime overhead coming from Go. As an alternative to this, you may compile Walk using an
+optional C implementation of the main message loop, by passing the `walk_use_cgo` build tag:
+
+   go build -tags walk_use_cgo
diff --git a/form.go b/form.go
@@ -392,34 +392,7 @@ func (fb *FormBase) Run() int {
 
 	fb.SetBoundsPixels(fb.BoundsPixels())
 
-	msg := (*win.MSG)(unsafe.Pointer(win.GlobalAlloc(0, unsafe.Sizeof(win.MSG{}))))
-	defer win.GlobalFree(win.HGLOBAL(unsafe.Pointer(msg)))
-
-	for fb.hWnd != 0 {
-		switch win.GetMessage(msg, 0, 0, 0) {
-		case 0:
-			return int(msg.WParam)
-
-		case -1:
-			return -1
-		}
-
-		switch msg.Message {
-		case win.WM_KEYDOWN:
-			if fb.handleKeyDown(msg) {
-				continue
-			}
-		}
-
-		if !win.IsDialogMessage(fb.hWnd, msg) {
-			win.TranslateMessage(msg)
-			win.DispatchMessage(msg)
-		}
-
-		runSynchronized()
-	}
-
-	return 0
+	return fb.mainLoop()
 }
 
 func (fb *FormBase) handleKeyDown(msg *win.MSG) bool {

diff --git a/mainloop_cgo.go b/mainloop_cgo.go
@@ -0,0 +1,56 @@
+// Copyright 2019 The Walk Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build windows,walk_use_cgo
+
+package walk
+
+import (
+	"unsafe"
+
+	"github.com/lxn/win"
+)
+
+// #include <windows.h>
+//
+// extern void shimRunSynchronized(void);
+// extern unsigned char shimHandleKeyDown(uintptr_t fb, uintptr_t m);
+//
+// static int mainloop(uintptr_t handle_ptr, uintptr_t fb_ptr)
+// {
+//     HANDLE *hwnd = (HANDLE *)handle_ptr;
+//     MSG m;
+//     int r;
+//
+//     while (*hwnd) {
+//         r = GetMessage(&m, NULL, 0, 0);
+//         if (!r)
+//             return m.wParam;
+//         else if (r < 0)
+//             return -1;
+//         if (m.message == WM_KEYDOWN && shimHandleKeyDown(fb_ptr, (uintptr_t)&m))
+//             continue;
+//         if (!IsDialogMessage(*hwnd, &m)) {
+//             TranslateMessage(&m);
+//             DispatchMessage(&m);
+//         }
+//         shimRunSynchronized();
+//     }
+//     return 0;
+// }
+import "C"
+
+//export shimHandleKeyDown
+func shimHandleKeyDown(fb uintptr, msg uintptr) bool {
+	return (*FormBase)(unsafe.Pointer(fb)).handleKeyDown((*win.MSG)(unsafe.Pointer(msg)))
+}
+
+//export shimRunSynchronized
+func shimRunSynchronized() {
+	runSynchronized()
+}
+
+func (fb *FormBase) mainLoop() int {
+	return int(C.mainloop(C.uintptr_t(uintptr(unsafe.Pointer(&fb.hWnd))), C.uintptr_t(uintptr(unsafe.Pointer(fb)))))
+}
diff --git a/mainloop_default.go b/mainloop_default.go
@@ -0,0 +1,43 @@
+// Copyright 2019 The Walk Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build windows,!walk_use_cgo
+
+package walk
+
+import (
+	"github.com/lxn/win"
+	"unsafe"
+)
+
+func (fb *FormBase) mainLoop() int {
+	msg := (*win.MSG)(unsafe.Pointer(win.GlobalAlloc(0, unsafe.Sizeof(win.MSG{}))))
+	defer win.GlobalFree(win.HGLOBAL(unsafe.Pointer(msg)))
+
+	for fb.hWnd != 0 {
+		switch win.GetMessage(msg, 0, 0, 0) {
+		case 0:
+			return int(msg.WParam)
+
+		case -1:
+			return -1
+		}
+
+		switch msg.Message {
+		case win.WM_KEYDOWN:
+			if fb.handleKeyDown(msg) {
+				continue
+			}
+		}
+
+		if !win.IsDialogMessage(fb.hWnd, msg) {
+			win.TranslateMessage(msg)
+			win.DispatchMessage(msg)
+		}
+
+		runSynchronized()
+	}
+
+	return 0
+}