From 2b48f7cabfbf269ac5d5ff292a7c788715ecd411 Mon Sep 17 00:00:00 2001
From: Pietro Gagliardi <pietro10@mac.com>
Date: Tue, 25 Mar 2014 09:10:06 -0400
Subject: [PATCH] Wrote the code to actually scroll Areas on Windows.

---
 area_windows.go     | 26 ++++++++++++++++++++++++--
 controls_windows.go |  1 -
 todo.md             |  1 +
 3 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/area_windows.go b/area_windows.go
index 4b4eedc..01080e5 100644
--- a/area_windows.go
+++ b/area_windows.go
@@ -51,6 +51,7 @@ func paintArea(s *sysData) {
 
 	var xrect _RECT
 	var ps _PAINTSTRUCT
+	var si _SCROLLINFO
 
 	// TODO send _TRUE if we want to erase the clip area
 	r1, _, _ := _getUpdateRect.Call(
@@ -61,15 +62,36 @@ func paintArea(s *sysData) {
 		return
 	}
 
+	si.cbSize = uint32(unsafe.Sizeof(si))
+	si.fMask = _SIF_POS | _SIF_TRACKPOS
+	r1, _, err := _getScrollInfo.Call(
+		uintptr(s.hwnd),
+		uintptr(_SB_HORZ),
+		uintptr(unsafe.Pointer(&si)))
+	if r1 == 0 {		// failure
+		panic(fmt.Errorf("error getting horizontal scroll position for Area repaint: %v", err))
+	}
+	hscroll := int(si.nPos)
+	si.cbSize = uint32(unsafe.Sizeof(si))			// MSDN example code reinitializes this each time, so we'll do it too just to be safe
+	si.fMask = _SIF_POS | _SIF_TRACKPOS
+	r1, _, err = _getScrollInfo.Call(
+		uintptr(s.hwnd),
+		uintptr(_SB_VERT),
+		uintptr(unsafe.Pointer(&si)))
+	if r1 == 0 {		// failure
+		panic(fmt.Errorf("error getting vertical scroll position for Area repaint: %v", err))
+	}
+	vscroll := int(si.nPos)
+
 	cliprect := image.Rect(int(xrect.Left), int(xrect.Top), int(xrect.Right), int(xrect.Bottom))
-	// TODO offset cliprect by scroll position
+	cliprect = cliprect.Add(image.Pt(hscroll, vscroll))		// adjust by scroll position
 	// make sure the cliprect doesn't fall outside the size of the Area
 	cliprect = cliprect.Intersect(image.Rect(0, 0, 320, 240))	// TODO change when adding resizing
 	if cliprect.Empty() {		// still no update rect
 		return
 	}
 
-	r1, _, err := _beginPaint.Call(
+	r1, _, err = _beginPaint.Call(
 		uintptr(s.hwnd),
 		uintptr(unsafe.Pointer(&ps)))
 	if r1 == 0 {		// failure
diff --git a/controls_windows.go b/controls_windows.go
index ab227ee..e7a72c9 100644
--- a/controls_windows.go
+++ b/controls_windows.go
@@ -501,7 +501,6 @@ const (
 
 var (
 	_getScrollInfo = user32.NewProc("GetScrollInfo")
-	_getScrollPos = user32.NewProc("GetScrollPos")
 	_setScrollInfo = user32.NewProc("SetScrollInfo")
 	_scrollWindowEx = user32.NewProc("ScrollWindowEx")
 )
diff --git a/todo.md b/todo.md
index aeaedaf..4a81bae 100644
--- a/todo.md
+++ b/todo.md
@@ -79,6 +79,7 @@ super ultra important things:
 - see update 18 March 2014 in README
 - resizing seems to be completely and totally broken in the Wayland backend
 - scrolling Areas in wine by clicking in the page scroll area often causes the main thread to lock up; uitask does not
+- make sure the first and last rows and columns of an Area are being drawn on Windows
 
 important things:
 - make specific wording in documentation consistent (make/create, etc.)