Remove borders and paddings from native controls on Linux (#14873)

* init

* update

* Update SpinInput.cpp

* possible fix for em_unit

* button alignment

* match titlebar height

* revert em_value for macOS and Windows

* Update GUI_Utils.hpp

* Merge branch 'main' into linux-black-borders-2

* Revert "button alignment"

This reverts commit 3fc7461071.

* Revert "match titlebar height"

This reverts commit c4aa1d9f1e.

* revert dpi changes

* match platform tags

* remove radio box borders

* Fix code indent

src/slic3r/GUI/PresetComboBoxes.cpp

@@ -865,6 +865,9 @@ PlaterPresetComboBox::PlaterPresetComboBox(wxWindow *parent, Preset::Type preset
         clr_picker = new wxBitmapButton(parent, wxID_ANY, {}, wxDefaultPosition, wxSize(FromDIP(20), FromDIP(20)), wxBU_EXACTFIT | wxBU_AUTODRAW | wxBORDER_NONE);
         clr_picker->SetBackgroundColour(StateColor::darkModeColorFor(*wxWHITE));
         clr_picker->SetToolTip(_L("Click to select filament color"));
+#ifdef __WXGTK__
+        RemoveButtonBorder(clr_picker);
+#endif
         clr_picker->Bind(wxEVT_BUTTON, [this](wxCommandEvent& e) {
             // Check if it's an official filament
             auto fila_type = Preset::remove_suffix_modified(GetValue().ToUTF8().data());