Just so things are clear, I am the current maintainer of gtk-engines.
This is a lot an issue that is a lot more complex than just "using transparency instead of drawing the window background color as part of the widget". We *need* to draw the background color in a lot of cases (GtkEntry, GtkProgressBar)! And I certainly would have removed all this if it was possible.
I don't want to go into too much detail here, but I would not be suprised if this is not fixable in GTK+. (I have not investigated this possibility too much.)
So this means the only way to achieve the correct behaviour would be to somehow work together and hint the engine/theme that filling the background is not necessary.
(Hm, I shouldn't missuse this bug to complain, but I do not like mozillas GTK+ emulation stuff in some ways. For example you could at least give the GtkWindow or the GtkFixed a name with gtk_widget_set_name to make it possible to create sane special cases for mozilla.)
Just so things are clear, I am the current maintainer of gtk-engines.
This is a lot an issue that is a lot more complex than just "using transparency instead of drawing the window background color as part of the widget". We *need* to draw the background color in a lot of cases (GtkEntry, GtkProgressBar)! And I certainly would have removed all this if it was possible.
I don't want to go into too much detail here, but I would not be suprised if this is not fixable in GTK+. (I have not investigated this possibility too much.)
So this means the only way to achieve the correct behaviour would be to somehow work together and hint the engine/theme that filling the background is not necessary.
(Hm, I shouldn't missuse this bug to complain, but I do not like mozillas GTK+ emulation stuff in some ways. For example you could at least give the GtkWindow or the GtkFixed a name with gtk_widget_set_name to make it possible to create sane special cases for mozilla.)