ui-imgui: Add basic initialization/deinitialization and renderning

For now, draw ImGui's demo window on top of the scene to see that
it works. Hook up the initialization/deinitialization to the glfw
part of the code. The same is done for emscripten, except don't
use the glfw emulation, as it's just one more intermediate layer.
Instead, skip the platform backend for now. All that's really needed
is input, and mostly mouse input. When enough of that is done, it
can be made into a proper backend for ImGui.

Signed-off-by: Alexander Shishkin <[email protected]>

core/CMakeLists.txt

@@ -86,7 +86,7 @@ set(ENGINE_SRC
     terrain.c ui.c scene.c font.c sound.c networking.c pngloader.c
     physics.c ui-animations.c input-fuzzer.c character.c settings.c
     gltf.c input-joystick.c render-gl.c mesh.c pipeline.c input-keyboard.c
-    game.c camera.c xyarray.c ca2d.c ca3d.c
+    game.c camera.c xyarray.c ca2d.c ca3d.c ui-imgui.c
     ${PLATFORM_SRC})
 
 # Mac OS X has deprecated OpenAL and is very vocal about it

core/clap.c

@@ -14,6 +14,7 @@
 #include "librarian.h"
 #include "physics.h"
 #include "settings.h"
+#include "ui-debug.h"
 #include "util.h"
 
 #ifdef HAVE_ASAN

core/display-glfw.c

@@ -7,6 +7,7 @@
 //#include <GL/glew.h>
 #include "display.h"
 #include <GLFW/glfw3.h>
+#include "ui-debug.h"
 #include "common.h"
 #include "input.h"
 #include "input-joystick.h"
@@ -174,6 +175,8 @@ void gl_init(const char *title, int w, int h, display_update update, void *updat
         ext = glGetStringi(GL_EXTENSIONS, i);
         msg("GL extension: '%s'\n", ext);
     }
+
+    imgui_init(window, width, height);
     // msg("GL initialized extensions: %s\n", exts);
 }
 
@@ -191,6 +194,7 @@ void gl_main_loop(void)
 
 void gl_done(void)
 {
+    imgui_done();
     glfwDestroyWindow(window);
     glfwTerminate();
 }

core/display-www.c

@@ -7,6 +7,7 @@
 #include "common.h"
 #include "display.h"
 #include "input-joystick.h"
+#include "ui-debug.h"
 
 static int width, height;
 
@@ -155,6 +156,7 @@ void gl_init(const char *title, int width, int height, display_update update_fn,
     msg("GL context: %d Extensions: '%s'\n", context, exts);
     EM_ASM(runtime_ready = true;);
     gl_get_sizes(NULL, NULL);
+    imgui_init(NULL, width, height);
     calc_refresh_rate(update_fn, data);
     //resize_fn(width, height);
 }

core/ui-debug.h

@@ -4,5 +4,8 @@
 
 void __ui_debug_printf(const char *mod, const char *fmt, ...);
 #define ui_debug_printf(args...) __ui_debug_printf(MODNAME, ## args)
+void imgui_init(void *data, int width, int height);
+void imgui_done(void);
+void imgui_render(int width, int height);
 
 #endif /* __CLAP_UI_DEBUG_H__ */

core/ui-imgui.c

@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: Apache-2.0
+#include "common.h"
+#include "ui-debug.h"
+
+#define CIMGUI_DEFINE_ENUMS_AND_STRUCTS
+#include "cimgui.h"
+
+#ifndef __EMSCRIPTEN__
+#include <GLFW/glfw3.h>
+#include "imgui_impl_glfw.h"
+#endif
+
+#include "imgui_impl_opengl3.h"
+
+static struct ImGuiContext *ctx;
+static struct ImGuiIO *io;
+
+void imgui_render(int width, int height)
+{
+    io->DisplaySize.x = width;
+    io->DisplaySize.y = height;
+
+    ImGui_ImplOpenGL3_NewFrame();
+#ifndef __EMSCRIPTEN__
+    ImGui_ImplGlfw_NewFrame();
+#endif
+    igNewFrame();
+
+    igSetNextWindowPos((struct ImVec2){0,0}, ImGuiCond_FirstUseEver,(struct ImVec2){0,0} );
+    igShowDemoWindow(NULL);
+
+    igRender();
+    ImGui_ImplOpenGL3_RenderDrawData(igGetDrawData());
+}
+
+void imgui_init(void *data, int width, int height)
+{
+    ctx = igCreateContext(NULL);
+    io = igGetIO();
+
+    io->DisplaySize.x = width;
+    io->DisplaySize.y = height;
+
+#ifndef __EMSCRIPTEN__
+    GLFWwindow *win = data;
+    ImGui_ImplGlfw_InitForOpenGL(win, true);
+    const char *glsl_version = "#version 410";
+#else
+    const char *glsl_version = "#version 300 es";
+#endif
+
+    ImGui_ImplOpenGL3_Init(glsl_version);
+
+    igStyleColorsDark(NULL);
+}
+
+void imgui_done(void)
+{
+    ImGui_ImplOpenGL3_Shutdown();
+#ifndef __EMSCRIPTEN__
+    ImGui_ImplGlfw_Shutdown();
+#endif
+    igDestroyContext(ctx);
+}

demo/ldjam56/onehandclap.c

@@ -163,6 +163,7 @@ EMSCRIPTEN_KEEPALIVE void renderFrame(void *data)
 
     s->proj_updated = 0;
     models_render(&ui.mq, NULL, NULL, NULL, NULL, 0, 0, &count);
+    imgui_render(s->width, s->height);
     PROF_STEP(ui, models);
 
     s->frames_total += frame_count;