[client] renderer/egl: implement support for rendering help text

The help text is rendered in the bottom left corner on a semi-transparent
background, very similar to how the FPS text is rendered.

client/renderers/EGL/help.c

@@ -0,0 +1,207 @@
+/*
+Looking Glass - KVM FrameRelay (KVMFR) Client
+Copyright (C) 2021 Guanzhong Chen <quantum2048@gmail.com>
+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 "help.h"
+#include "common/debug.h"
+
+#include "texture.h"
+#include "shader.h"
+#include "model.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+// these headers are auto generated by cmake
+#include "help.vert.h"
+#include "help.frag.h"
+#include "help_bg.frag.h"
+
+struct EGL_Help
+{
+  const LG_Font * font;
+  LG_FontObj      fontObj;
+
+  EGL_Texture   * texture;
+  EGL_Shader    * shader;
+  EGL_Shader    * shaderBG;
+  EGL_Model     * model;
+  LG_FontBitmap * bmp;
+
+  bool  shouldRender;
+  int   iwidth, iheight;
+  float width, height;
+
+  // uniforms
+  GLint uScreen  , uSize;
+  GLint uScreenBG, uSizeBG;
+};
+
+bool egl_help_init(EGL_Help ** help, const LG_Font * font, LG_FontObj fontObj)
+{
+  *help = (EGL_Help *)malloc(sizeof(EGL_Help));
+  if (!*help)
+  {
+    DEBUG_ERROR("Failed to malloc EGL_Help");
+    return false;
+  }
+
+  memset(*help, 0, sizeof(EGL_Help));
+
+  (*help)->font    = font;
+  (*help)->fontObj = fontObj;
+
+  if (!egl_texture_init(&(*help)->texture, NULL))
+  {
+    DEBUG_ERROR("Failed to initialize the help texture");
+    return false;
+  }
+
+  if (!egl_shader_init(&(*help)->shader))
+  {
+    DEBUG_ERROR("Failed to initialize the help shader");
+    return false;
+  }
+
+  if (!egl_shader_init(&(*help)->shaderBG))
+  {
+    DEBUG_ERROR("Failed to initialize the help bg shader");
+    return false;
+  }
+
+
+  if (!egl_shader_compile((*help)->shader,
+        b_shader_help_vert, b_shader_help_vert_size,
+        b_shader_help_frag, b_shader_help_frag_size))
+  {
+    DEBUG_ERROR("Failed to compile the help shader");
+    return false;
+  }
+
+  if (!egl_shader_compile((*help)->shaderBG,
+        b_shader_help_vert   , b_shader_help_vert_size,
+        b_shader_help_bg_frag, b_shader_help_bg_frag_size))
+  {
+    DEBUG_ERROR("Failed to compile the help shader");
+    return false;
+  }
+
+
+  (*help)->uSize     = egl_shader_get_uniform_location((*help)->shader  , "size"  );
+  (*help)->uScreen   = egl_shader_get_uniform_location((*help)->shader  , "screen");
+  (*help)->uSizeBG   = egl_shader_get_uniform_location((*help)->shaderBG, "size"  );
+  (*help)->uScreenBG = egl_shader_get_uniform_location((*help)->shaderBG, "screen");
+
+  if (!egl_model_init(&(*help)->model))
+  {
+    DEBUG_ERROR("Failed to initialize the fps model");
+    return false;
+  }
+
+  egl_model_set_default((*help)->model);
+  egl_model_set_texture((*help)->model, (*help)->texture);
+
+  return true;
+}
+
+void egl_help_free(EGL_Help ** help)
+{
+  if (!*help)
+    return;
+
+  egl_texture_free(&(*help)->texture );
+  egl_shader_free (&(*help)->shader  );
+  egl_shader_free (&(*help)->shaderBG);
+  egl_model_free  (&(*help)->model   );
+
+  free(*help);
+  *help = NULL;
+}
+
+void egl_help_set_text(EGL_Help * help, const char * help_text)
+{
+  if (!help_text)
+  {
+    help->shouldRender = false;
+    return;
+  }
+
+  help->bmp = help->font->render(help->fontObj, 0xffffff00, help_text);
+  if (!help->bmp)
+  {
+    DEBUG_ERROR("Failed to render help text");
+    return;
+  }
+}
+
+void egl_help_render(EGL_Help * help, const float scaleX, const float scaleY)
+{
+  if (help->bmp)
+  {
+    if (help->iwidth != help->bmp->width || help->iheight != help->bmp->height)
+    {
+      help->iwidth  = help->bmp->width;
+      help->iheight = help->bmp->height;
+      help->width   = (float)help->bmp->width;
+      help->height  = (float)help->bmp->height;
+
+      egl_texture_setup(
+        help->texture,
+        EGL_PF_BGRA,
+        help->bmp->width ,
+        help->bmp->height,
+        help->bmp->width * help->bmp->bpp,
+        false,
+        false
+      );
+    }
+
+    egl_texture_update
+    (
+      help->texture,
+      help->bmp->pixels
+    );
+
+    help->shouldRender = true;
+    help->font->release(help->fontObj, help->bmp);
+    help->bmp = NULL;
+  }
+
+  if (!help->shouldRender)
+    return;
+
+  glEnable(GL_BLEND);
+  glBlendColor(0, 0, 0, 0.5);
+  glBlendFunc(GL_CONSTANT_ALPHA, GL_ONE_MINUS_CONSTANT_ALPHA);
+
+  // render the background first
+  egl_shader_use(help->shaderBG);
+  glUniform2f(help->uScreenBG, scaleX     , scaleY      );
+  glUniform2f(help->uSizeBG  , help->width, help->height);
+  egl_model_render(help->model);
+
+  glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+
+  // render the texture over the background
+  egl_shader_use(help->shader);
+  glUniform2f(help->uScreen, scaleX     , scaleY      );
+  glUniform2f(help->uSize  , help->width, help->height);
+  egl_model_render(help->model);
+
+  glDisable(GL_BLEND);
+}