I am trying to port my application from linux to windows and I have a problem with theming. In linux this works out of a box, just compile it and application is using good theme and looks native.

I have installed gtkmm3 and gtk3 in MSYS2 and I am building it with CMake. This is OK, I had to copy all dlls to directory with binary to be able to execute it. I did not copy anything else. I am trying to create "unzip and execute" package.

My problem is, that application looks out of place. It does not look native at all. There are shadows around the window, which is fine in Windows10, but in Windows 7 it looks not native. Also several icons are missing.

Even gitk3-demo looks non-native in the same way (but it has at least the minimize/maximize/close icons correct).

So the question is: How can I achieve native look of GTK3 application on Windows? Or at least native window decorations?

Thanks

Thera are two sub-problems: missing icons and setting right theme.

Missing icons

For missing icons it was enough to copy these icons

window-close-symbolic.symbolic.png
window-maximize-symbolic.symbolic.png
window-minimize-symbolic.symbolic.png

from: C:\msys64\mingw32\share\icons\Adwaita\22x22\actions

to: "your executable folder"\share\icons\Adwaita\22x22\actions

Theme

Using win32 native theme

There is actually a built-in native-like theme in GTK3. For using native-like theme just create file "your executable folder"\etc\gtk-3.0\settings.ini with this in it

[Settings]
gtk-theme-name=win32

win32 theme is built in into GTK3 and only three icons from previous step seems to be needed.

On windows 7 this looks as following:

The problem is, that the decorations looks the same even on Windows 10 (including window decorations).

From comment from @andlabs : GTK+ 3 uses the uxtheme.dll APIs to get its Windows look and feel, and unfortunately Microsoft has kept those Windows 7-like for window borders. (more in comments)

You can see Windows 10 Gtk3 application with win32 theme here:

Using non default theme

And if you are not happy with default or win32 theme, you can use custom themes (like this Flat-Pat) from the internet. :) In order to do it you need to create config file:

"your executable folder"\etc\gtk-3.0\settings.ini with this in it

[Settings]
gtk-theme-name=Flat-Plat

and you need to copy the theme files to directory in path of your executable

"your executable folder"\share\themes\Flat-Plat

in that folder, the index.theme file and gtk-x.x folders should be present. Obviously gtk-theme-name and folder name should match.

After you run the executable you should be able to get different theme.

EDIT: So there is a win32 theme built-in, thank you @andlabs

EDIT2: Added screenshots

EDIT3: Added Windows 10 screenshot and corrected facts.

You can set GTK_CSD=0 environment variable to disable client-side window decorations and enable Windows native decorations, which gets rid of the ugly win7-like titlebar, as well as Adwaita-like one.

For people like me who use (activestate) perl, the /share and /etc need to be placed one directory above the perl.exe (say in C:\Perl64 if perl.exe is in C:\Perl64\bin).

While GTK_CSD=0 is doing a fine job for windows frame icons, it seams that default Drag-And-Drop (DND) icons are missing too.

Dragging GtkEntry or GtkTreeView contents shows a drag-icon.

I've prepared a button as drag source under Gtk+-3.24.4. When dragging the button, the mouse cursor disappears and no drag icon is shown.

When using gtk_drag_source_set_icon_pixbuf(bt, pixbuf), the pixbuf appears as drag icon. But doing it this way is only half the job done, because move/copy indicators are missing on the icon.

Actually, Gtk+3 been compatible with Windows 10 and you can use the native windows theme by making this your default theme.