From 150b999c0a8a19b5f841a32f1add4c663c533f22 Mon Sep 17 00:00:00 2001
From: Pietro Gagliardi <pietro10@mac.com>
Date: Wed, 2 Apr 2014 13:47:11 -0400
Subject: [PATCH] Forced Common Controls version 6 on Windows by embedding the
 needed manifest in.

---
 comctl_windows.go | 100 ++++++++++++++++++++++++++++++++++++++++++++--
 common_windows.go |   2 +-
 2 files changed, 97 insertions(+), 5 deletions(-)

diff --git a/comctl_windows.go b/comctl_windows.go
index 8e3522a..7c336be 100644
--- a/comctl_windows.go
+++ b/comctl_windows.go
@@ -4,14 +4,18 @@ package ui
 
 import (
 	"fmt"
-//	"syscall"
+	"syscall"
 	"unsafe"
+	"io/ioutil"
 )
 
 // pretty much every constant here except _WM_USER is from commctrl.h
 // TODO for all: filter out constants not available in Windows XP
 
-// TODO ensure that comctl32.dll version 6 or newer is loaded as it provides marquee progress bars
+var (
+	// TODO deinitialize at program end?
+	comctlManifestCookie uintptr
+)
 
 // InitCommonControlsEx constants.
 const (
@@ -35,18 +39,82 @@ const (
 )
 
 var (
-	_initCommonControlsEx = comctl32.NewProc("InitCommonControlsEx")
+	_activateActCtx = kernel32.NewProc("ActivateActCtx")
+	_createActCtx = kernel32.NewProc("CreateActCtxW")
 )
 
+/*
+Windows requires a manifest file to enable Common Controls version 6.
+The only way to not require an external manifest is to synthesize the manifest ourselves.
+We can use the activation context API to load it at runtime.
+References:
+- http://stackoverflow.com/questions/4308503/how-to-enable-visual-styles-without-a-manifest
+- http://support.microsoft.com/kb/830033
+*/
+func forceCommonControls6() (err error) {
+	var (
+		// from winbase.h; var because Go won't let me convert this constant
+		_INVALID_HANDLE_VALUE = -1
+	)
+
+	manifestfile, err := ioutil.TempFile("", "gouicomctl32v6manifest")
+	if err != nil {
+		return fmt.Errorf("error creating synthesized manifest file: %v", err)
+	}
+	_, err = manifestfile.Write(manifest)
+	if err != nil {
+		return fmt.Errorf("error writing synthesized manifest file: %v", err)
+	}
+	filename := manifestfile.Name()
+	// we now have to close the file, otherwise ActivateActCtx() will complain that it's in use by another program
+	// if ioutil.TempFile() ever changes so that the file is deleted when it is closed, this will need to change
+	manifestfile.Close()
+
+	var actctx struct {
+		cbSize				uint32
+		dwFlags				uint32
+		lpSource				*uint16
+		wProcessorArchitecture	uint16
+		wLangId				uint16		// originally LANGID
+		lpAssemblyDirectory	uintptr		// originally LPCWSTR
+		lpResourceName		uintptr		// originally LPCWSTR
+		lpApplicationName		uintptr		// originally LPCWSTR
+		hModule				_HANDLE		// originally HMODULE
+	}
+
+	actctx.cbSize = uint32(unsafe.Sizeof(actctx))
+	// TODO set ACTCTX_FLAG_SET_PROCESS_DEFAULT? I can't find a reference to figure out what this means
+	actctx.lpSource = syscall.StringToUTF16Ptr(filename)
+
+	r1, _, err := _createActCtx.Call(uintptr(unsafe.Pointer(&actctx)))
+	if r1 == uintptr(_INVALID_HANDLE_VALUE) {		// failure
+		return fmt.Errorf("error creating activation context for synthesized manifest file: %v", err)
+	}
+	r1, _, err = _activateActCtx.Call(
+		r1,
+		uintptr(unsafe.Pointer(&comctlManifestCookie)))
+	if r1 == uintptr(_FALSE) {		// failure
+		return fmt.Errorf("error activating activation context for synthesized manifest file: %v", err)
+	}
+	return nil
+}
+
 func initCommonControls() (err error) {
 	var icc struct {
 		dwSize	uint32
 		dwICC	uint32
 	}
 
+	err = forceCommonControls6()
+	if err != nil {
+		return fmt.Errorf("error forcing Common Controls version 6 (or newer): %v", err)
+	}
+
 	icc.dwSize = uint32(unsafe.Sizeof(icc))
 	icc.dwICC = _ICC_PROGRESS_CLASS
-	r1, _, err := _initCommonControlsEx.Call(uintptr(unsafe.Pointer(&icc)))
+
+	comctl32 = syscall.NewLazyDLL("comctl32.dll")
+	r1, _, err := comctl32.NewProc("InitCommonControlsEx").Call(uintptr(unsafe.Pointer(&icc)))
 	if r1 == _FALSE {		// failure
 		// TODO does it set GetLastError()?
 		return fmt.Errorf("error initializing Common Controls (comctl32.dll): %v", err)
@@ -87,3 +155,27 @@ const (
 	_PBM_SETBKCOLOR = _CCM_SETBKCOLOR
 	_PBM_SETMARQUEE = (_WM_USER + 10)
 )
+
+var manifest = []byte(`<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
+<assemblyIdentity
+    version="1.0.0.0"
+    processorArchitecture="*"
+    name="CompanyName.ProductName.YourApplication"
+    type="win32"
+/>
+<description>Your application description here.</description>
+<dependency>
+    <dependentAssembly>
+        <assemblyIdentity
+            type="win32"
+            name="Microsoft.Windows.Common-Controls"
+            version="6.0.0.0"
+            processorArchitecture="*"
+            publicKeyToken="6595b64144ccf1df"
+            language="*"
+        />
+    </dependentAssembly>
+</dependency>
+</assembly>
+`)
diff --git a/common_windows.go b/common_windows.go
index acc3b2e..522b65a 100644
--- a/common_windows.go
+++ b/common_windows.go
@@ -11,7 +11,7 @@ var (
 	user32 = syscall.NewLazyDLL("user32.dll")
 	kernel32 = syscall.NewLazyDLL("kernel32.dll")
 	gdi32 = syscall.NewLazyDLL("gdi32.dll")
-	comctl32 = syscall.NewLazyDLL("comctl32.dll")
+	comctl32 *syscall.LazyDLL		// comctl32 not defined here; see comctl_windows.go
 	gdiplus = syscall.NewLazyDLL("gdiplus.dll")
 )