ImGuiAdjust.hh

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#ifndef IMGUI_ADJUST_HH
#define IMGUI_ADJUST_HH
 
#include "ImGuiPartInterface.hh"
 
#include "gl_vec.hh"
 
namespace openmsx {
 
// Keep the imgui window in the 'same' position in the main view port (= the
// main openMSX window) when that view port changes size. This happens when
// changing scale_factor, but also when switching to/from fullscreen.
//
// Without this adjustment, after the resize, the window can e.g. move from the
// border to somewhere in the middle of the view port, or even outside the view
// port. This is not desired for stuff like the OSD icons or the reverse-bar.
//
// The heuristic for keeping the window in the 'same' position is:
// * Only make adjustment when the window is shown fully inside the main view port.
// * Separately for the horizontal and vertical direction:
// * Check if the window is closer to the left or the right (or top or bottom)
//   border of the viewport.
// * Keep this closet distance the same after rescaling. In other words, if the
//   window was e.g. close to the bottom, it will remain near the bottom.
// * And some stuff for boundary conditions, see comments in the code for details.
class AdjustWindowInMainViewPort
{
public:
        // should be called right before the call to im::Window()
        void pre();
 
        // should be called right after the call to im::Window()
        bool post();
 
        void save(ImGuiTextBuffer& buf);
        bool loadLine(std::string_view name, zstring_view value);
 
private:
        gl::vec2 oldViewPortSize;
        gl::vec2 oldRelWindowPos;
        bool oldIsOnMainViewPort = false;
        bool setMainViewPort = false;
 
        static constexpr auto persistentElements = std::tuple{
                PersistentElement{"viewPortSize",   &AdjustWindowInMainViewPort::oldViewPortSize},
                PersistentElement{"windowPos",      &AdjustWindowInMainViewPort::oldRelWindowPos},
                PersistentElement{"onMainViewPort", &AdjustWindowInMainViewPort::oldIsOnMainViewPort}
        };
};
 
} // namespace openmsx
 
#endif