1 files changed, 69 insertions, 0 deletions
diff --git a/prev/container_windows.go b/prev/container_windows.go
new file mode 100644
index 0000000..953d108
--- /dev/null
+++ b/prev/container_windows.go
@@ -0,0 +1,69 @@
+// 4 august 2014
+
+package ui
+
+// #include "winapi_windows.h"
+import "C"
+
+type sizing struct {
+	sizingbase
+
+	// for size calculations
+	baseX           C.int
+	baseY           C.int
+	internalLeading C.LONG // for Label; see Label.commitResize() for details
+
+	// for the actual resizing
+	// possibly the HDWP
+}
+
+// For Windows, Microsoft just hands you a list of preferred control sizes as part of the MSDN documentation and tells you to roll with it.
+// These sizes are given in "dialog units", which are independent of the font in use.
+// We need to convert these into standard pixels, which requires we get the device context of the OS window.
+// References:
+// - http://msdn.microsoft.com/en-us/library/ms645502%28VS.85%29.aspx - the calculation needed
+// - http://support.microsoft.com/kb/125681 - to get the base X and Y
+// (thanks to http://stackoverflow.com/questions/58620/default-button-size)
+// In my tests (see https://github.com/andlabs/windlgunits), the GetTextExtentPoint32() option for getting the base X produces much more accurate results than the tmAveCharWidth option when tested against the sample values given in http://msdn.microsoft.com/en-us/library/windows/desktop/dn742486.aspx#sizingandspacing, but can be off by a pixel in either direction (probably due to rounding errors).
+
+// note on MulDiv():
+// div will not be 0 in the usages below
+// we also ignore overflow; that isn't likely to happen for our use case anytime soon
+
+func fromdlgunitsX(du int, d *sizing) int {
+	return int(C.MulDiv(C.int(du), d.baseX, 4))
+}
+
+func fromdlgunitsY(du int, d *sizing) int {
+	return int(C.MulDiv(C.int(du), d.baseY, 8))
+}
+
+const (
+	// shared by multiple containers
+	marginDialogUnits  = 7
+	paddingDialogUnits = 4
+)
+
+func beginResize(hwnd C.HWND) (d *sizing) {
+	var baseX, baseY C.int
+	var internalLeading C.LONG
+
+	d = new(sizing)
+
+	C.calculateBaseUnits(hwnd, &baseX, &baseY, &internalLeading)
+	d.baseX = baseX
+	d.baseY = baseY
+	d.internalLeading = internalLeading
+
+	d.xpadding = fromdlgunitsX(paddingDialogUnits, d)
+	d.ypadding = fromdlgunitsY(paddingDialogUnits, d)
+
+	return d
+}
+
+func marginRectDLU(r *C.RECT, top int, bottom int, left int, right int, d *sizing) {
+	r.left += C.LONG(fromdlgunitsX(left, d))
+	r.top += C.LONG(fromdlgunitsY(top, d))
+	r.right -= C.LONG(fromdlgunitsX(right, d))
+	r.bottom -= C.LONG(fromdlgunitsY(bottom, d))
+}