Build with gtk3

.github/workflows/tests.yml

@@ -26,7 +26,7 @@ jobs:
       if: matrix.ui == 'gui'
       env:
         HOMEBREW_NO_INSTALL_CLEANUP: 1
-      run: brew install gtk+
+      run: brew install gtk+3
     - name: configure
       run: |
           set +x
@@ -85,7 +85,7 @@ jobs:
         install: git diffutils make pkg-config mingw-w64-${{ matrix.arch }}-glib2 mingw-w64-${{ matrix.arch }}-gcc mingw-w64-${{ matrix.arch }}-ghostscript mingw-w64-${{ matrix.arch }}-ntldd-git man zip
     - name: install GUI prereqs
       if: matrix.ui == 'gui'
-      run: pacman -S --noconfirm mingw-w64-${{ matrix.arch }}-gtk2
+      run: pacman -S --noconfirm mingw-w64-${{ matrix.arch }}-gtk3
     - name: git config
       run: git config --global core.autocrlf input
       shell: bash
@@ -146,7 +146,7 @@ jobs:
       if: matrix.ui == 'gui'
       env:
         DEBIAN_FRONTEND: noninteractive
-      run: sudo apt-get install -y libgtk2.0-dev
+      run: sudo apt-get install -y libgtk-3-dev
     - name: configure
       run: |
           echo ./configure ${{ matrix.clionly }} ${{ matrix.debugprintf }} --with-werror