Icon: Assume default icon size is always 16x16

win.GetSystemMetricsForDpi() ignores dpi parameter prior Windows 10. It
returns 16x16, or 24x24, or 32x32 depending on "zoom" set by user.
Assume the default small icon size is always 16x16 at 96dpi.

Reverts: 8f6d762
See-also: #636
Signed-off-by: Simon Rozman <simon@rozman.si>

Author: rozmansi

icon.go

@@ -17,6 +17,8 @@ import (
 	"github.com/lxn/win"
 )
 
+var defaultIconSize96dpi = Size{16, 16}
+
 // Icon is a bitmap that supports transparency and combining multiple
 // variants of an image in different resolutions.
 type Icon struct {
@@ -77,7 +79,7 @@ func IconShield() *Icon {
 }
 
 func stockIcon(id uintptr) *Icon {
-	return &Icon{res: win.MAKEINTRESOURCE(id), size96dpi: defaultIconSize(), isStock: true}
+	return &Icon{res: win.MAKEINTRESOURCE(id), size96dpi: defaultIconSize96dpi, isStock: true}
 }
 
 // NewIconFromFile returns a new Icon, using the specified icon image file and default size.
@@ -88,7 +90,7 @@ func NewIconFromFile(filePath string) (*Icon, error) {
 // NewIconFromFileWithSize returns a new Icon, using the specified icon image file and size.
 func NewIconFromFileWithSize(filePath string, size Size) (*Icon, error) {
 	if size.Width == 0 || size.Height == 0 {
-		size = defaultIconSize()
+		size = defaultIconSize96dpi
 	}
 
 	return checkNewIcon(&Icon{filePath: filePath, size96dpi: size})
@@ -116,7 +118,7 @@ func NewIconFromResourceIdWithSize(id int, size Size) (*Icon, error) {
 
 func newIconFromResource(res *uint16, size Size) (*Icon, error) {
 	if size.Width == 0 || size.Height == 0 {
-		size = defaultIconSize()
+		size = defaultIconSize96dpi
 	}
 
 	return checkNewIcon(&Icon{res: res, size96dpi: size})
@@ -271,7 +273,7 @@ func (i *Icon) handleForDPIWithError(dpi int) (win.HICON, error) {
 	var size Size
 	if i.size96dpi.Width == 0 || i.size96dpi.Height == 0 {
 		flags |= win.LR_DEFAULTSIZE
-		size = SizeFrom96DPI(defaultIconSize(), dpi)
+		size = SizeFrom96DPI(defaultIconSize96dpi, dpi)
 	} else {
 		size = SizeFrom96DPI(i.size96dpi, dpi)
 	}
@@ -416,8 +418,3 @@ func sizeFromHICON(hIcon win.HICON) (Size, error) {
 
 	return Size{int(bi.BmiHeader.BiWidth), int(bi.BmiHeader.BiHeight)}, nil
 }
-
-// defaultIconSize returns default small icon size in 1/92" units.
-func defaultIconSize() Size {
-	return Size{int(win.GetSystemMetricsForDpi(win.SM_CXSMICON, 96)), int(win.GetSystemMetricsForDpi(win.SM_CYSMICON, 96))}
-}