merge doublemelon (#2067)

non-exhaustive (but exhausting) list of changes:

* base laid for multiple window support, but will likely require more work to work correctly
* encapsulation of frontend state for proper multi-instance support
* (JIT still needs a fix for the NDS::Current workaround but we can get there later)
* new, more flexible configuration system

src/frontend/ScreenLayout.h

@@ -0,0 +1,104 @@
+/*
+    Copyright 2016-2023 melonDS team
+
+    This file is part of melonDS.
+
+    melonDS is free software: you can redistribute it and/or modify it under
+    the terms of the GNU General Public License as published by the Free
+    Software Foundation, either version 3 of the License, or (at your option)
+    any later version.
+
+    melonDS is distributed in the hope that it will be useful, but WITHOUT ANY
+    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+    FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with melonDS. If not, see http://www.gnu.org/licenses/.
+*/
+
+#ifndef SCREENLAYOUT_H
+#define SCREENLAYOUT_H
+
+enum ScreenLayoutType
+{
+    screenLayout_Natural, // top screen above bottom screen always
+    screenLayout_Horizontal,
+    screenLayout_Vertical,
+    screenLayout_Hybrid,
+    screenLayout_MAX,
+};
+
+enum ScreenRotation
+{
+    screenRot_0Deg,
+    screenRot_90Deg,
+    screenRot_180Deg,
+    screenRot_270Deg,
+    screenRot_MAX,
+};
+
+enum ScreenSizing
+{
+    screenSizing_Even, // both screens get same size
+    screenSizing_EmphTop, // make top screen as big as possible, fit bottom screen in remaining space
+    screenSizing_EmphBot,
+    screenSizing_Auto, // not applied in SetupScreenLayout
+    screenSizing_TopOnly,
+    screenSizing_BotOnly,
+    screenSizing_MAX,
+};
+
+const int kMaxScreenTransforms = 3;
+
+class ScreenLayout
+{
+public:
+    ScreenLayout();
+    ~ScreenLayout() {}
+
+    // setup the display layout based on the provided display size and parameters
+    // * screenWidth/screenHeight: size of the host display
+    // * screenLayout: how the DS screens are laid out
+    // * rotation: angle at which the DS screens are presented
+    // * sizing: how the display size is shared between the two screens
+    // * screenGap: size of the gap between the two screens in pixels
+    // * integerScale: force screens to be scaled up at integer scaling factors
+    // * screenSwap: whether to swap the position of both screens
+    // * topAspect/botAspect: ratio by which to scale the top and bottom screen respectively
+    void Setup(int screenWidth, int screenHeight,
+               ScreenLayoutType screenLayout,
+               ScreenRotation rotation,
+               ScreenSizing sizing,
+               int screenGap,
+               bool integerScale,
+               bool swapScreens,
+               float topAspect, float botAspect);
+
+    // get a 2x3 transform matrix for each screen and whether it's a top or bottom screen
+    // note: the transform assumes an origin point at the top left of the display,
+    // X going right and Y going down
+    // for each screen the source coordinates should be (0,0) and (256,192)
+    // 'out' should point to an array of 6*MaxScreenTransforms floats
+    // 'kind' should point to an array of MaxScreenTransforms ints
+    // (0 = indicates top screen, 1 = bottom screen)
+    // returns the amount of screens
+    int GetScreenTransforms(float* out, int* kind);
+
+    // de-transform the provided host display coordinates to get coordinates
+    // on the bottom screen
+    bool GetTouchCoords(int& x, int& y, bool clamp);
+
+private:
+    float TopScreenMtx[6];
+    float BotScreenMtx[6];
+    float HybScreenMtx[6];
+    float TouchMtx[6];
+    float HybTouchMtx[6];
+    bool TopEnable;
+    bool BotEnable;
+    bool HybEnable;
+    int HybScreen;
+    int HybPrevTouchScreen; // 0:unknown, 1:buttom screen, 2:hybrid screen
+};
+
+#endif // SCREENLAYOUT_H