GUI: prepare for multiple render backends

I want to see whether I can bind OpenGL to this thing

src/gui/render/abstract.cpp

@@ -0,0 +1,79 @@
+/**
+ * Furnace Tracker - multi-system chiptune tracker
+ * Copyright (C) 2021-2023 tildearrow and contributors
+ *
+ * This program 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 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "../gui.h"
+
+bool FurnaceGUIRender::lockTexture(void* which, void** data, int* pitch) {
+  return false;
+}
+
+bool FurnaceGUIRender::unlockTexture(void* which) {
+  return false;
+}
+
+bool FurnaceGUIRender::updateTexture(void* which, void* data, int pitch) {
+  return false;
+}
+
+void* FurnaceGUIRender::createTexture(bool dynamic, int width, int height) {
+  return NULL;
+}
+
+bool FurnaceGUIRender::destroyTexture(void* which) {
+  return false;
+}
+
+void FurnaceGUIRender::setTextureBlendMode(void* which, FurnaceGUIBlendMode mode) {
+}
+
+void FurnaceGUIRender::setBlendMode(FurnaceGUIBlendMode mode) {
+}
+
+void FurnaceGUIRender::clear(ImVec4 color) {
+}
+
+void FurnaceGUIRender::renderGUI() {
+}
+
+void FurnaceGUIRender::wipe(float alpha) {
+}
+
+void FurnaceGUIRender::present() {
+}
+
+bool FurnaceGUIRender::getOutputSize(int& w, int& h) {
+  return false;
+}
+
+bool FurnaceGUIRender::init(SDL_Window* win) {
+  return false;
+}
+
+void FurnaceGUIRender::initGUI(SDL_Window* win) {
+}
+
+bool FurnaceGUIRender::quit() {
+  return false;
+}
+
+void FurnaceGUIRender::quitGUI(){ 
+}
+
+FurnaceGUIRender::~FurnaceGUIRender() {
+}

src/gui/render/renderSDL.cpp

@@ -0,0 +1,123 @@
+/**
+ * Furnace Tracker - multi-system chiptune tracker
+ * Copyright (C) 2021-2023 tildearrow and contributors
+ *
+ * This program 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 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "renderSDL.h"
+
+bool FurnaceGUIRenderSDL::lockTexture(void* which, void** data, int* pitch) {
+  return SDL_LockTexture((SDL_Texture*)which,NULL,data,pitch)==0;
+}
+
+bool FurnaceGUIRenderSDL::unlockTexture(void* which) {
+  SDL_UnlockTexture((SDL_Texture*)which);
+  return true;
+}
+
+bool FurnaceGUIRenderSDL::updateTexture(void* which, void* data, int pitch) {
+  return SDL_UpdateTexture((SDL_Texture*)which,NULL,data,pitch)==0;
+}
+
+void* FurnaceGUIRenderSDL::createTexture(bool dynamic, int width, int height) {
+  return SDL_CreateTexture(sdlRend,SDL_PIXELFORMAT_ABGR8888,dynamic?SDL_TEXTUREACCESS_STREAMING:SDL_TEXTUREACCESS_STATIC,width,height);
+}
+
+bool FurnaceGUIRenderSDL::destroyTexture(void* which) {
+  SDL_DestroyTexture((SDL_Texture*)which);
+  return true;
+}
+
+void FurnaceGUIRenderSDL::setTextureBlendMode(void* which, FurnaceGUIBlendMode mode) {
+  switch (mode) {
+    case GUI_BLEND_MODE_NONE:
+      SDL_SetTextureBlendMode((SDL_Texture*)which,SDL_BLENDMODE_NONE);
+      break;
+    case GUI_BLEND_MODE_BLEND:
+      SDL_SetTextureBlendMode((SDL_Texture*)which,SDL_BLENDMODE_BLEND);
+      break;
+    case GUI_BLEND_MODE_ADD:
+      SDL_SetTextureBlendMode((SDL_Texture*)which,SDL_BLENDMODE_ADD);
+      break;
+    case GUI_BLEND_MODE_MULTIPLY:
+      SDL_SetTextureBlendMode((SDL_Texture*)which,SDL_BLENDMODE_MOD);
+      break;
+  }
+}
+
+void FurnaceGUIRenderSDL::setBlendMode(FurnaceGUIBlendMode mode) {
+  switch (mode) {
+    case GUI_BLEND_MODE_NONE:
+      SDL_SetRenderDrawBlendMode(sdlRend,SDL_BLENDMODE_NONE);
+      break;
+    case GUI_BLEND_MODE_BLEND:
+      SDL_SetRenderDrawBlendMode(sdlRend,SDL_BLENDMODE_BLEND);
+      break;
+    case GUI_BLEND_MODE_ADD:
+      SDL_SetRenderDrawBlendMode(sdlRend,SDL_BLENDMODE_ADD);
+      break;
+    case GUI_BLEND_MODE_MULTIPLY:
+      SDL_SetRenderDrawBlendMode(sdlRend,SDL_BLENDMODE_MOD);
+      break;
+  }
+}
+
+void FurnaceGUIRenderSDL::clear(ImVec4 color) {
+  SDL_SetRenderDrawColor(sdlRend,color.x*255,color.y*255,color.z*255,color.w*255);
+  SDL_RenderClear(sdlRend);
+}
+
+void FurnaceGUIRenderSDL::renderGUI() {
+  ImGui_ImplSDLRenderer_RenderDrawData(ImGui::GetDrawData());
+}
+
+void FurnaceGUIRenderSDL::wipe(float alpha) {
+  SDL_SetRenderDrawBlendMode(sdlRend,SDL_BLENDMODE_BLEND);
+  SDL_SetRenderDrawColor(sdlRend,0,0,0,255*alpha);
+  SDL_RenderFillRect(sdlRend,NULL);
+}
+
+void FurnaceGUIRenderSDL::present() {
+  SDL_RenderPresent(sdlRend);
+}
+
+bool FurnaceGUIRenderSDL::getOutputSize(int& w, int& h) {
+  return SDL_GetRendererOutputSize(sdlRend,&w,&h)==0;
+}
+
+bool FurnaceGUIRenderSDL::init(SDL_Window* win) {
+  sdlRend=SDL_CreateRenderer(win,-1,SDL_RENDERER_ACCELERATED|SDL_RENDERER_PRESENTVSYNC|SDL_RENDERER_TARGETTEXTURE);
+  return (sdlRend!=NULL);
+}
+
+void FurnaceGUIRenderSDL::initGUI(SDL_Window* win) {
+  IMGUI_CHECKVERSION();
+  ImGui::CreateContext();
+
+  ImGui_ImplSDL2_InitForSDLRenderer(win,sdlRend);
+  ImGui_ImplSDLRenderer_Init(sdlRend);
+}
+
+void FurnaceGUIRenderSDL::quitGUI() {
+  ImGui_ImplSDLRenderer_Shutdown();
+}
+
+bool FurnaceGUIRenderSDL::quit() {
+  if (sdlRend==NULL) return false;
+  SDL_DestroyRenderer(sdlRend);
+  sdlRend=NULL;
+  return true;
+}

src/gui/render/renderSDL.h

@@ -0,0 +1,43 @@
+/**
+ * Furnace Tracker - multi-system chiptune tracker
+ * Copyright (C) 2021-2023 tildearrow and contributors
+ *
+ * This program 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 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "../gui.h"
+
+class FurnaceGUIRenderSDL: public FurnaceGUIRender {
+  SDL_Renderer* sdlRend;
+  public:
+    bool lockTexture(void* which, void** data, int* pitch);
+    bool unlockTexture(void* which);
+    bool updateTexture(void* which, void* data, int pitch);
+    void* createTexture(bool dynamic, int width, int height);
+    bool destroyTexture(void* which);
+    void setTextureBlendMode(void* which, FurnaceGUIBlendMode mode);
+    void setBlendMode(FurnaceGUIBlendMode mode);
+    void clear(ImVec4 color);
+    void renderGUI();
+    void wipe(float alpha);
+    void present();
+    bool getOutputSize(int& w, int& h);
+    bool init(SDL_Window* win);
+    void initGUI(SDL_Window* win);
+    void quitGUI();
+    bool quit();
+    FurnaceGUIRenderSDL():
+      sdlRend(NULL) {}
+};