[client] imgui: use improved high DPI rendering

This actually makes imgui render at a higher resolution, avoiding scaling
and resulting blurriness.

client/CMakeLists.txt

@@ -121,6 +121,7 @@ set(SOURCES
 	src/egl_dynprocs.c
 	src/eglutil.c
 	src/overlay_utils.c
+	src/overlay_utils.cpp
 
 	src/overlay/fps.c
 	src/overlay/graphs.c

client/include/overlay_utils.h

@@ -23,6 +23,15 @@
 
 #include "common/types.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 void overlayGetImGuiRect(struct Rect * rect);
+void imGuiResetStyle(void);
+
+#ifdef __cplusplus
+}
+#endif
 
 #endif

client/include/util.h

@@ -46,4 +46,7 @@ static inline double util_clamp(double x, double min, double max)
   return x;
 }
 
+#define DEFAULT_FONT_NAME "DejaVu Sans Mono"
+char * util_getUIFont(const char * fontName);
+
 #endif

client/renderers/EGL/egl.c

@@ -504,6 +504,10 @@ void egl_on_resize(void * opaque, const int width, const int height, const doubl
   damage->count = 0;
   free(atomic_exchange(&this->desktopDamage, damage));
 
+  // this is needed to refresh the font atlas texture
+  ImGui_ImplOpenGL3_Shutdown();
+  ImGui_ImplOpenGL3_NewFrame();
+
   egl_damage_resize(this->damage, this->translateX, this->translateY, this->scaleX, this->scaleY);
 }
 

client/renderers/OpenGL/opengl.c

@@ -354,6 +354,10 @@ void opengl_on_resize(void * opaque, const int width, const int height, const do
       1.0f
     );
   }
+
+  // this is needed to refresh the font atlas texture
+  ImGui_ImplOpenGL2_Shutdown();
+  ImGui_ImplOpenGL2_NewFrame();
 }
 
 bool opengl_on_mouse_shape(void * opaque, const LG_RendererCursor cursor,

client/src/app.c

@@ -677,14 +677,6 @@ int app_renderOverlay(struct Rect * rects, int maxRects)
     const int written =
       overlay->ops->render(overlay->udata, false, buffer, MAX_OVERLAY_RECTS);
 
-    for (int i = 0; i < written; ++i)
-    {
-      buffer[i].x *= g_state.windowScale;
-      buffer[i].y *= g_state.windowScale;
-      buffer[i].w *= g_state.windowScale;
-      buffer[i].h *= g_state.windowScale;
-    }
-
     // It is an error to run out of rectangles, because we will not be able to
     // correctly calculate the damage of the next frame.
     assert(written >= 0);

client/src/main.c

@@ -56,6 +56,8 @@
 #include "ll.h"
 #include "egl_dynprocs.h"
 #include "overlays.h"
+#include "overlay_utils.h"
+#include "util.h"
 
 // forwards
 static int cursorThread(void * unused);
@@ -180,14 +182,18 @@ static int renderThread(void * unused)
     if (resize)
     {
       g_state.io->DisplaySize = (ImVec2) {
-        .x = g_state.windowW,
-        .y = g_state.windowH
-      };
-      g_state.io->DisplayFramebufferScale = (ImVec2) {
-        .x = g_state.windowScale,
-        .y = g_state.windowScale,
+        .x = g_state.windowW * g_state.windowScale,
+        .y = g_state.windowH * g_state.windowScale
       };
 
+      imGuiResetStyle();
+      ImGuiStyle_ScaleAllSizes(g_state.style, g_state.windowScale);
+
+      ImFontAtlas_Clear(g_state.io->Fonts);
+      ImFontAtlas_AddFontFromFileTTF(g_state.io->Fonts, g_state.fontName,
+        14 * g_state.windowScale, NULL, NULL);
+      ImFontAtlas_Build(g_state.io->Fonts);
+
       if (g_state.lgr)
         g_state.lgr->on_resize(g_state.lgrData, g_state.windowW, g_state.windowH,
             g_state.windowScale, g_state.dstRect, g_params.winRotate);
@@ -755,12 +761,18 @@ static int lg_run(void)
 
   /* setup imgui */
   igCreateContext(NULL);
-  g_state.io = igGetIO();
+  g_state.io    = igGetIO();
+  g_state.style = igGetStyle();
+
   unsigned char *text_pixels = NULL;
   int text_w, text_h;
   ImFontAtlas_GetTexDataAsRGBA32(g_state.io->Fonts, &text_pixels,
       &text_w, &text_h, NULL);
 
+  g_state.windowScale = 1.0;
+  g_state.fontName    = util_getUIFont(DEFAULT_FONT_NAME);
+  DEBUG_INFO("Using font: %s", g_state.fontName);
+
   g_state.overlays = ll_new();
   app_registerOverlay(&LGOverlayFPS   , NULL);
   app_registerOverlay(&LGOverlayGraphs, NULL);
@@ -1149,6 +1161,7 @@ static void lg_shutdown(void)
   ringbuffer_free(&g_state.renderTimings);
   ringbuffer_free(&g_state.frameTimings );
 
+  free(g_state.fontName);
   igDestroyContext(NULL);
 }
 

client/src/main.h

@@ -47,8 +47,10 @@ struct AppState
 {
   enum RunState state;
 
-  ImGuiIO   * io;
-  struct ll * overlays;
+  ImGuiIO    * io;
+  ImGuiStyle * style;
+  struct ll  * overlays;
+  char       * fontName;
 
   struct LG_DisplayServerOps * ds;
   bool                         dsInitialized;

client/src/overlay/graphs.c

@@ -93,6 +93,8 @@ static int graphs_render(void * udata, bool interactive,
   if (!g_state.showTiming)
     return 0;
 
+  float fontSize = igGetFontSize();
+
   ImVec2 pos = {0.0f, 0.0f};
   igSetNextWindowBgAlpha(0.4f);
   igSetNextWindowPos(pos, 0, pos);
@@ -121,7 +123,7 @@ static int graphs_render(void * udata, bool interactive,
     }
 
     char  title[64];
-    const ImVec2 size = {400.0f, 100.0f};
+    const ImVec2 size = {28.0f * fontSize, 7.0f * fontSize};
 
     snprintf(title, sizeof(title),
         "%s: min:%4.2f max:%4.2f avg:%4.2f/%4.2fHz",

client/src/overlay_utils.cpp

@@ -0,0 +1,28 @@
+/**
+ * Looking Glass
+ * Copyright (C) 2017-2021 The Looking Glass Authors
+ * https://looking-glass.io
+ *
+ * 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., 59
+ * Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include "overlay_utils.h"
+
+#include "imgui.h"
+
+void imGuiResetStyle(void)
+{
+  ImGui::GetStyle() = ImGuiStyle();
+}

client/src/util.c

@@ -29,6 +29,7 @@
 #include <string.h>
 #include <assert.h>
 #include <math.h>
+#include <fontconfig/fontconfig.h>
 
 bool util_fileGetContents(const char * filename, char ** buffer, size_t * length)
 {
@@ -258,3 +259,48 @@ int util_mergeOverlappingRects(FrameDamageRect * out, const FrameDamageRect * re
       out[o++] = out[i];
   return o;
 }
+
+char * util_getUIFont(const char * fontName)
+{
+  static FcConfig * fc = NULL;
+  char * ttf = NULL;
+
+  if (!fc)
+    fc = FcInitLoadConfigAndFonts();
+
+  if (!fc)
+  {
+    DEBUG_ERROR("FcInitLoadConfigAndFonts Failed");
+    return NULL;
+  }
+
+  FcPattern * pat = FcNameParse((const FcChar8*) fontName);
+  if (!pat)
+  {
+    DEBUG_ERROR("FCNameParse failed");
+    return NULL;
+  }
+
+  FcConfigSubstitute(fc, pat, FcMatchPattern);
+  FcDefaultSubstitute(pat);
+  FcResult result;
+  FcChar8 * file = NULL;
+  FcPattern * match = FcFontMatch(fc, pat, &result);
+
+  if (!match)
+  {
+    DEBUG_ERROR("FcFontMatch Failed");
+    goto fail_parse;
+  }
+
+  if (FcPatternGetString(match, FC_FILE, 0, &file) == FcResultMatch)
+    ttf = strdup((char *) file);
+  else
+    DEBUG_ERROR("Failed to locate the requested font: %s", fontName);
+
+  FcPatternDestroy(match);
+
+fail_parse:
+  FcPatternDestroy(pat);
+  return ttf;
+}