GUI: prepare for multiple render backends

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

CMakeLists.txt

@@ -587,6 +587,10 @@ extern/igfd/ImGuiFileDialog.cpp
 
 src/gui/plot_nolerp.cpp
 
+src/gui/render.cpp
+src/gui/render/abstract.cpp
+src/gui/render/renderSDL.cpp
+
 src/gui/font_exo.cpp
 src/gui/font_liberationSans.cpp
 src/gui/font_mononoki.cpp

src/gui/chanOsc.cpp

@@ -152,10 +152,10 @@ void FurnaceGUI::drawChanOsc() {
 
       if (chanOscUseGrad) {
         if (chanOscGradTex==NULL) {
-          chanOscGradTex=SDL_CreateTexture(sdlRend,SDL_PIXELFORMAT_ABGR8888,SDL_TEXTUREACCESS_STREAMING,chanOscGrad.width,chanOscGrad.height);
+          chanOscGradTex=rend->createTexture(true,chanOscGrad.width,chanOscGrad.height);
 
           if (chanOscGradTex==NULL) {
-            logE("error while creating gradient texture! %s",SDL_GetError());
+            logE("error while creating gradient texture!");
           } else {
             updateChanOscGradTex=true;
           }
@@ -170,10 +170,10 @@ void FurnaceGUI::drawChanOsc() {
           if (chanOscGradTex!=NULL) {
             if (updateChanOscGradTex) {
               chanOscGrad.render();
-              if (SDL_UpdateTexture(chanOscGradTex,NULL,chanOscGrad.grad.get(),chanOscGrad.width*4)==0) {
+              if (rend->updateTexture(chanOscGradTex,chanOscGrad.grad.get(),chanOscGrad.width*4)) {
                 updateChanOscGradTex=false;
               } else {
-                logE("error while updating gradient texture! %s",SDL_GetError());
+                logE("error while updating gradient texture!");
               }
             }
 

src/gui/gui.cpp

@@ -3537,8 +3537,8 @@ bool FurnaceGUI::loop() {
       }
     }
     // update canvas size as well
-    if (SDL_GetRendererOutputSize(sdlRend,&canvasW,&canvasH)!=0) {
+    if (!rend->getOutputSize(canvasW,canvasH)) {
-      logW("loop: error while getting output size! %s",SDL_GetError());
+      logW("loop: error while getting output size!");
     } else {
       //logV("updateWindow: canvas size %dx%d",canvasW,canvasH);
       // and therefore window size
@@ -4418,7 +4418,7 @@ bool FurnaceGUI::loop() {
       portrait=(scrW<scrH);
       logV("portrait: %d (%dx%d)",portrait,scrW,scrH);
 
-      SDL_GetRendererOutputSize(sdlRend,&canvasW,&canvasH);
+      rend->getOutputSize(canvasW,canvasH);
 #endif
       if (patternOpen) nextWindow=GUI_WINDOW_PATTERN;
 #ifdef __APPLE__
@@ -5796,30 +5796,24 @@ bool FurnaceGUI::loop() {
       }
     }
 
-    SDL_SetRenderDrawColor(sdlRend,uiColors[GUI_COLOR_BACKGROUND].x*255,
+    rend->clear(uiColors[GUI_COLOR_BACKGROUND]);
-                                   uiColors[GUI_COLOR_BACKGROUND].y*255,
-                                   uiColors[GUI_COLOR_BACKGROUND].z*255,
-                                   uiColors[GUI_COLOR_BACKGROUND].w*255);
-    SDL_RenderClear(sdlRend);
     renderTimeBegin=SDL_GetPerformanceCounter();
     ImGui::Render();
     renderTimeEnd=SDL_GetPerformanceCounter();
-    ImGui_ImplSDLRenderer_RenderDrawData(ImGui::GetDrawData());
+    rend->renderGUI();
     if (mustClear) {
-      SDL_RenderClear(sdlRend);
+      rend->clear(ImVec4(0,0,0,0));
       mustClear--;
     } else {
       if (initialScreenWipe>0.0f && !settings.disableFadeIn) {
         WAKE_UP;
         initialScreenWipe-=ImGui::GetIO().DeltaTime*5.0f;
         if (initialScreenWipe>0.0f) {
-          SDL_SetRenderDrawBlendMode(sdlRend,SDL_BLENDMODE_BLEND);
+          rend->wipe(pow(initialScreenWipe,2.0f));
-          SDL_SetRenderDrawColor(sdlRend,0,0,0,255*pow(initialScreenWipe,2.0f));
-          SDL_RenderFillRect(sdlRend,NULL);
         }
       }
     }
-    SDL_RenderPresent(sdlRend);
+    rend->present();
 
     layoutTimeDelta=layoutTimeEnd-layoutTimeBegin;
     renderTimeDelta=renderTimeEnd-renderTimeBegin;
@@ -6186,22 +6180,27 @@ bool FurnaceGUI::init() {
     SDL_SetHint(SDL_HINT_RENDER_DRIVER,settings.renderDriver.c_str());
   }
 
-  sdlRend=SDL_CreateRenderer(sdlWin,-1,SDL_RENDERER_ACCELERATED|SDL_RENDERER_PRESENTVSYNC|SDL_RENDERER_TARGETTEXTURE);
+  if (!initRender()) {
-
+    if (settings.renderBackend=="OpenGL") {
-  if (sdlRend==NULL) {
+      settings.renderBackend="";
-    lastError=fmt::sprintf("could not init renderer! %s",SDL_GetError());
+      e->setConf("renderBackend","");
-    if (!settings.renderDriver.empty()) {
-      settings.renderDriver="";
-      e->setConf("renderDriver","");
       e->saveConf();
-      lastError=fmt::sprintf("\r\nthe render driver has been set to a safe value. please restart Furnace.");
+      lastError=fmt::sprintf("\r\nthe render backend has been set to a safe value. please restart Furnace.");
+    } else {
+      lastError=fmt::sprintf("could not init renderer! %s",SDL_GetError());
+      if (!settings.renderDriver.empty()) {
+        settings.renderDriver="";
+        e->setConf("renderDriver","");
+        e->saveConf();
+        lastError=fmt::sprintf("\r\nthe render driver has been set to a safe value. please restart Furnace.");
+      }
     }
     return false;
   }
 
   // try acquiring the canvas size
-  if (SDL_GetRendererOutputSize(sdlRend,&canvasW,&canvasH)!=0) {
+  if (!rend->getOutputSize(canvasW,canvasH)) {
-    logW("could not get renderer output size! %s",SDL_GetError());
+    logW("could not get renderer output size!");
   } else {
     logV("canvas size: %dx%d",canvasW,canvasH);
   }
@@ -6213,11 +6212,7 @@ bool FurnaceGUI::init() {
     }
   }
 
-  IMGUI_CHECKVERSION();
+  rend->initGUI(sdlWin);
-  ImGui::CreateContext();
-
-  ImGui_ImplSDL2_InitForSDLRenderer(sdlWin,sdlRend);
-  ImGui_ImplSDLRenderer_Init(sdlRend);
 
   applyUISettings();
 
@@ -6439,10 +6434,10 @@ void FurnaceGUI::commitState() {
 
 bool FurnaceGUI::finish() {
   commitState();
-  ImGui_ImplSDLRenderer_Shutdown();
+  rend->quitGUI();
   ImGui_ImplSDL2_Shutdown();
   ImGui::DestroyContext();
-  SDL_DestroyRenderer(sdlRend);
+  quitRender();
   SDL_DestroyWindow(sdlWin);
 
   if (vibrator) {
@@ -6463,7 +6458,6 @@ bool FurnaceGUI::finish() {
 FurnaceGUI::FurnaceGUI():
   e(NULL),
   sdlWin(NULL),
-  sdlRend(NULL),
   vibrator(NULL),
   vibratorAvailable(false),
   sampleTex(NULL),

src/gui/gui.h

@@ -70,6 +70,11 @@
 
 #define FM_PREVIEW_SIZE 512
 
+enum FurnaceGUIRenderBackend {
+  GUI_BACKEND_SDL=0,
+  GUI_BACKEND_GL
+};
+
 // TODO:
 // - add colors for FM envelope and waveform
 // - maybe add "alternate" color for FM modulators/carriers (a bit difficult)
@@ -1191,7 +1196,7 @@ struct FurnaceGUIQueryResult {
 
 struct FurnaceGUIImage {
   unsigned char* data;
-  SDL_Texture* tex;
+  void* tex;
   int width, height, ch;
 
   FurnaceGUIImage():
@@ -1213,15 +1218,45 @@ struct FurnaceGUIPerfMetric {
     elapsed(0) {}
 };
 
+enum FurnaceGUIBlendMode {
+  GUI_BLEND_MODE_NONE=0,
+  GUI_BLEND_MODE_BLEND,
+  GUI_BLEND_MODE_ADD,
+  GUI_BLEND_MODE_MULTIPLY
+};
+
+class FurnaceGUIRender {
+  public:
+    virtual bool lockTexture(void* which, void** data, int* pitch);
+    virtual bool unlockTexture(void* which);
+    virtual bool updateTexture(void* which, void* data, int pitch);
+    virtual void* createTexture(bool dynamic, int width, int height);
+    virtual bool destroyTexture(void* which);
+    virtual void setTextureBlendMode(void* which, FurnaceGUIBlendMode mode);
+    virtual void setBlendMode(FurnaceGUIBlendMode mode);
+    virtual void clear(ImVec4 color);
+    virtual void renderGUI();
+    virtual void wipe(float alpha);
+    virtual void present();
+    virtual bool getOutputSize(int& w, int& h);
+    virtual bool init(SDL_Window* win);
+    virtual void initGUI(SDL_Window* win);
+    virtual void quitGUI();
+    virtual bool quit();
+    virtual ~FurnaceGUIRender();
+};
+
 class FurnaceGUI {
   DivEngine* e;
 
+  FurnaceGUIRenderBackend renderBackend;
+  FurnaceGUIRender* rend;
+
   SDL_Window* sdlWin;
-  SDL_Renderer* sdlRend;
   SDL_Haptic* vibrator;
   bool vibratorAvailable;
   
-  SDL_Texture* sampleTex;
+  void* sampleTex;
   int sampleTexW, sampleTexH;
   bool updateSampleTex;
 
@@ -1454,6 +1489,7 @@ class FurnaceGUI {
     String midiInDevice;
     String midiOutDevice;
     String c163Name;
+    String renderBackend;
     String renderDriver;
     String initialSysName;
     String noteOffLabel;
@@ -1601,6 +1637,7 @@ class FurnaceGUI {
       midiInDevice(""),
       midiOutDevice(""),
       c163Name(""),
+      renderBackend(""),
       renderDriver(""),
       initialSysName("Sega Genesis/Mega Drive"),
       noteOffLabel("OFF"),
@@ -1887,7 +1924,7 @@ class FurnaceGUI {
   bool chanOscWaveCorr, chanOscOptions, updateChanOscGradTex, chanOscUseGrad;
   ImVec4 chanOscColor;
   Gradient2D chanOscGrad;
-  SDL_Texture* chanOscGradTex;
+  void* chanOscGradTex;
   float chanOscLP0[DIV_MAX_CHANS];
   float chanOscLP1[DIV_MAX_CHANS];
   float chanOscVol[DIV_MAX_CHANS];
@@ -2040,7 +2077,7 @@ class FurnaceGUI {
   void highlightWindow(const char* winName);
 
   FurnaceGUIImage* getImage(FurnaceGUIImages image);
-  SDL_Texture* getTexture(FurnaceGUIImages image, SDL_BlendMode blendMode=SDL_BLENDMODE_BLEND);
+  void* getTexture(FurnaceGUIImages image, FurnaceGUIBlendMode blendMode=GUI_BLEND_MODE_BLEND);
   void drawImage(ImDrawList* dl, FurnaceGUIImages image, const ImVec2& pos, const ImVec2& scale, double rotate, const ImVec2& uvMin, const ImVec2& uvMax, const ImVec4& imgColor);
 
   void drawMobileControls();
@@ -2189,6 +2226,9 @@ class FurnaceGUI {
   String encodeKeyMap(std::map<int,int>& map);
   void decodeKeyMap(std::map<int,int>& map, String source);
 
+  bool initRender();
+  bool quitRender();
+
   const char* getSystemName(DivSystem which);
 
   public:

src/gui/image.cpp

@@ -49,7 +49,7 @@ const unsigned int imageLen[GUI_IMAGE_MAX]={
   image_pat_size
 };
 
-SDL_Texture* FurnaceGUI::getTexture(FurnaceGUIImages image, SDL_BlendMode blendMode) {
+void* FurnaceGUI::getTexture(FurnaceGUIImages image, FurnaceGUIBlendMode blendMode) {
   FurnaceGUIImage* img=getImage(image);
 
   if (img==NULL) return NULL;
@@ -57,14 +57,14 @@ SDL_Texture* FurnaceGUI::getTexture(FurnaceGUIImages image, SDL_BlendMode blendM
   if (img->width<=0 || img->height<=0) return NULL;
 
   if (img->tex==NULL) {
-    img->tex=SDL_CreateTexture(sdlRend,SDL_PIXELFORMAT_ABGR8888,SDL_TEXTUREACCESS_STATIC,img->width,img->height);
+    img->tex=rend->createTexture(false,img->width,img->height);
     if (img->tex==NULL) {
       logE("error while creating image %d texture! %s",(int)image,SDL_GetError());
       return NULL;
     }
-    SDL_SetTextureBlendMode(img->tex,blendMode);
+    rend->setTextureBlendMode(img->tex,blendMode);
 
-    if (SDL_UpdateTexture(img->tex,NULL,img->data,img->width*4)!=0) {
+    if (!rend->updateTexture(img->tex,img->data,img->width*4)) {
       logE("error while updating texture of image %d! %s",(int)image,SDL_GetError());
     }
   }

src/gui/intro.cpp

@@ -24,7 +24,7 @@
 
 void FurnaceGUI::drawImage(ImDrawList* dl, FurnaceGUIImages image, const ImVec2& pos, const ImVec2& scale, double rotate, const ImVec2& uvMin, const ImVec2& uvMax, const ImVec4& imgColor) {
   FurnaceGUIImage* imgI=getImage(image);
-  SDL_Texture* img=getTexture(image);
+  void* img=getTexture(image);
 
   float squareSize=MAX(introMax.x-introMin.x,introMax.y-introMin.y);
   float uDiff=uvMax.x-uvMin.x;
@@ -162,7 +162,7 @@ void FurnaceGUI::drawIntro(double introTime, bool monitor) {
         getTexture(GUI_IMAGE_TALOGO);
         getTexture(GUI_IMAGE_TACHIP);
         getTexture(GUI_IMAGE_LOGO);
-        getTexture(GUI_IMAGE_INTROBG,SDL_BLENDMODE_ADD);
+        getTexture(GUI_IMAGE_INTROBG,GUI_BLEND_MODE_ADD);
 
         if (monitor) {
           ImVec2 textPos=ImLerp(top,bottom,ImVec2(0.5,0.5));

src/gui/pattern.cpp

@@ -49,11 +49,11 @@ void _popPartBlend(const ImDrawList* drawList, const ImDrawCmd* cmd) {
 }
 
 void FurnaceGUI::pushPartBlend() {
-  SDL_SetRenderDrawBlendMode(sdlRend,SDL_BLENDMODE_ADD);
+  rend->setBlendMode(GUI_BLEND_MODE_ADD);
 }
 
 void FurnaceGUI::popPartBlend() {
-  SDL_SetRenderDrawBlendMode(sdlRend,SDL_BLENDMODE_BLEND);
+  rend->setBlendMode(GUI_BLEND_MODE_BLEND);
 }
 
 // draw a pattern row

src/gui/render.cpp

@@ -0,0 +1,36 @@
+/**
+ * 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"
+#include "render/renderSDL.h"
+
+bool FurnaceGUI::initRender() {
+  if (rend!=NULL) return false;
+  
+  rend=new FurnaceGUIRenderSDL;
+  return rend->init(sdlWin);
+}
+
+bool FurnaceGUI::quitRender() {
+  if (rend==NULL) return false;
+  bool ret=rend->quit();
+  delete rend;
+  rend=NULL;
+  return ret;
+}

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) {}
+};

src/gui/sampleEdit.cpp

@@ -1110,12 +1110,12 @@ void FurnaceGUI::drawSampleEdit() {
 
       if (sampleTex==NULL || sampleTexW!=avail.x || sampleTexH!=avail.y) {
         if (sampleTex!=NULL) {
-          SDL_DestroyTexture(sampleTex);
+          rend->destroyTexture(sampleTex);
           sampleTex=NULL;
         }
         if (avail.x>=1 && avail.y>=1) {
           logD("recreating sample texture.");
-          sampleTex=SDL_CreateTexture(sdlRend,SDL_PIXELFORMAT_ABGR8888,SDL_TEXTUREACCESS_STREAMING,avail.x,avail.y);
+          sampleTex=rend->createTexture(true,avail.x,avail.y);
           sampleTexW=avail.x;
           sampleTexH=avail.y;
           if (sampleTex==NULL) {
@@ -1131,7 +1131,7 @@ void FurnaceGUI::drawSampleEdit() {
           unsigned int* dataT=NULL;
           int pitch=0;
           logD("updating sample texture.");
-          if (SDL_LockTexture(sampleTex,NULL,(void**)&dataT,&pitch)!=0) {
+          if (!rend->lockTexture(sampleTex,(void**)&dataT,&pitch)) {
             logE("error while locking sample texture! %s",SDL_GetError());
           } else {
             unsigned int* data=new unsigned int[sampleTexW*sampleTexH];
@@ -1217,7 +1217,7 @@ void FurnaceGUI::drawSampleEdit() {
             }
 
             memcpy(dataT,data,sampleTexW*sampleTexH*sizeof(unsigned int));
-            SDL_UnlockTexture(sampleTex);
+            rend->unlockTexture(sampleTex);
             delete[] data;
           }
           updateSampleTex=false;