1 files changed, 122 insertions, 0 deletions
diff --git a/prefsize_windows.go b/prefsize_windows.go
index cb44f2c..07a633f 100644
--- a/prefsize_windows.go
+++ b/prefsize_windows.go
@@ -71,6 +71,7 @@ var stdDlgSizes = [nctypes]dlgunits{
 
 var (
 	_selectObject = gdi32.NewProc("SelectObject")
+	_getTextExtentPoint32 = gdi32.NewProc("GetTextExtentPoint32W")
 	_getTextMetrics = gdi32.NewProc("GetTextMetricsW")
 	_getWindowDC = user32.NewProc("GetWindowDC")
 	_releaseDC = user32.NewProc("ReleaseDC")
@@ -149,6 +150,127 @@ func muldiv(ma int, mb int, div int) int {
 	return int(int32(r1))
 }
 
+// List Boxes do not dynamically handle horizontal scrollbars.
+// We have to manually handle this ourselves.
+// TODO make this run on the main thread when we switch to uitask taking function literals
+// TODO this is inefficient; some caching would be nice
+func recalcListboxWidth(hwnd _HWND) {
+	var size _SIZE
+
+	ret := make(chan uiret)
+	defer close(ret)
+	uitask <- &uimsg{
+		call:		_sendMessage,
+		p:		[]uintptr{
+			uintptr(hwnd),
+			uintptr(_LB_GETCOUNT),
+			uintptr(0),
+			uintptr(0),
+		},
+		ret:		ret,
+	}
+	r := <-ret
+	if r.ret == uintptr(_LB_ERR) {		// failure
+		panic(fmt.Errorf("error getting number of items for Listbox width calculations: %v", r.err))
+	}
+	n := int(r.ret)
+	uitask <- &uimsg{
+		call:		_getWindowDC,
+		p:		[]uintptr{uintptr(hwnd)},
+		ret:		ret,
+	}
+	r = <-ret
+	if r.ret == 0 {		// failure
+		panic(fmt.Errorf("error getting DC for Listbox width calculations: %v", r.err))
+	}
+	dc := _HANDLE(r.ret)
+	uitask <- &uimsg{
+		call:		_selectObject,
+		p:		[]uintptr{
+			uintptr(dc),
+			uintptr(controlFont),
+		},
+		ret:		ret,
+	}
+	r = <-ret
+	if r.ret == 0  {		// failure
+		panic(fmt.Errorf("error loading control font into device context for Listbox width calculation: %v", r.err))
+	}
+	hextent := uintptr(0)
+	for i := 0; i < n; i++ {
+		uitask <- &uimsg{
+			call:		_sendMessage,
+			p:		[]uintptr{
+				uintptr(hwnd),
+				uintptr(_LB_GETTEXTLEN),
+				uintptr(_WPARAM(i)),
+				uintptr(0),
+			},
+			ret:		ret,
+		}
+		r := <-ret
+		if r.ret == uintptr(_LB_ERR) {
+			panic("UI library internal error: LB_ERR from LB_GETTEXTLEN in what we know is a valid listbox index (came from LB_GETSELITEMS)")
+		}
+		str := make([]uint16, r.ret)
+		uitask <- &uimsg{
+			call:		_sendMessage,
+			p:		[]uintptr{
+				uintptr(hwnd),
+				uintptr(_LB_GETTEXT),
+				uintptr(_WPARAM(i)),
+				uintptr(_LPARAM(unsafe.Pointer(&str[0]))),
+			},
+			ret:		ret,
+		}
+		r = <-ret
+		if r.ret == uintptr(_LB_ERR) {
+			panic("UI library internal error: LB_ERR from LB_GETTEXT in what we know is a valid listbox index (came from LB_GETSELITEMS)")
+		}
+		// r.ret is still the length of the string; this time without the null terminator
+		uitask <- &uimsg{
+			call:		_getTextExtentPoint32,
+			p:		[]uintptr{
+				uintptr(dc),
+				uintptr(unsafe.Pointer(&str[0])),
+				r.ret,
+				uintptr(unsafe.Pointer(&size)),
+			},
+			ret:		ret,
+		}
+		r = <-ret
+		if r.ret == 0 {		// failure
+			panic(fmt.Errorf("error getting width of item %d text for Listbox width calculation: %v", i, r.err))
+		}
+		if hextent < uintptr(size.cx) {
+			hextent = uintptr(size.cx)
+		}
+	}
+	uitask <- &uimsg{
+		call:		_releaseDC,
+		p:		[]uintptr{
+			uintptr(hwnd),
+			uintptr(dc),
+		},
+		ret:		ret,
+	}
+	r = <-ret
+	if r.ret == 0 {		// failure
+		panic(fmt.Errorf("error releasing DC for Listbox width calculations: %v", r.err))
+	}
+	uitask <- &uimsg{
+		call:		_sendMessage,
+		p:		[]uintptr{
+			uintptr(hwnd),
+			uintptr(_LB_SETHORIZONTALEXTENT),
+			hextent,
+			uintptr(0),
+		},
+		ret:		ret,
+	}
+	<-ret
+}
+
 type _SIZE struct {
 	cx	int32		// originally LONG
 	cy	int32