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Glview Widgets

This widget renders OpenGL in an elementary object, which hides Evas GL complexity.

Table of Contents

Adding a Glview

Create a GLView widget with the elm_glview_add() function. 

Evas_Object *glview = elm_glview_add(parent);

In this example, the size of the GLView is set to 200×200 pixels. 

elm_glview_size_set(glview, 200, 200);

Using GLView API

We can configure the GLView rendering mode by activating the following rendering modes:

ELM_GLVIEW_ALPHA Alpha channel enabled rendering mode. ELM_GLVIEW_DEPTH Depth buffer enabled rendering mode (24 bits by default)
ELM_GLVIEW_STENCIL Stencil buffer enabled rendering mode (8 bits by default) ELM_GLVIEW_DIRECT Request direct rendering, unless there must be a fallback.
ELM_GLVIEW_CLIENT_SIDE_ROTATIONClient will handle GL view rotation if direct rendering is enabled.ELM_GLVIEW_DEPTH_8 Request min.
8 bits for the depth buffer
ELM_GLVIEW_DEPTH_16 Request min.
16 bits for the depth buffer 		ELM_GLVIEW_DEPTH_24 Request min.
24 bits for the depth buffer (default)
ELM_GLVIEW_DEPTH_32 Request min.
32 bits for the depth buffer 		ELM_GLVIEW_STENCIL_1 Request min.
1 bits for the stencil buffer
ELM_GLVIEW_STENCIL_2 Request min.
2 bits for the stencil buffer 		ELM_GLVIEW_STENCIL_4 Request min.
4 bits for the stencil buffer
ELM_GLVIEW_STENCIL_8 Request min.
8 bits for the stencil buffer (default) 		ELM_GLVIEW_STENCIL_16 Request min.
16 bits for the stencil buffer
ELM_GLVIEW_MULTISAMPLE_LOW MSAA with minimum number of samples. ELM_GLVIEW_MULTISAMPLE_MED MSAA with half the number of maximum samples.
ELM_GLVIEW_MULTISAMPLE_HIGH MSAA with maximum number of samples.

In this example, we enable alpha channel and depth buffer rendering mode. 

elm_glview_mode_set(glview, ELM_GLVIEW_ALPHA | ELM_GLVIEW_DEPTH);

We decide what to do with the GL surface when the GLView widget is resized. 

elm_glview_resize_policy_set(glview, ELM_GLVIEW_RESIZE_POLICY_RECREATE);

The GL surface is destroyed and recreated to the new size (default function). The resize policy can also be set to ELM_GLVIEW_RESIZE_POLICY_SCALE. In that case, only the image object is scaled, not the underlying GL surface.

This is how to set the GLView rendering policy. 

elm_glview_render_policy_set(glview, ELM_GLVIEW_RENDER_POLICY_ALWAYS);

The glview object is always redrawn during the rendering loop. It can also be set to ELM_GLVIEW_RENDER_POLICY_ON_DEMAND (default function), where glview widget is redrawn only when it is visible.

We can register callbacks: 

elm_glview_init_func_set(glview, _init_gl_cb);
elm_glview_del_func_set(glview, _del_gl_cb);
elm_glview_resize_func_set(glview, _resize_gl_cb);
elm_glview_render_func_set(glview, _draw_gl_cb);

elm_glview_init_func_set() registers an init callback that is called at the GLView object creation.

elm_glview_del_func_set() registers a del function that is called when the GLView object is deleted.

elm_glview_resize_func_set() registers the resize function that is called during the rendering loop when the GLView object is resized.

elm_glview_render_func_set() registers the render function that is called when the GLView object must be redrawn.

Using GLView Callbacks

GLView widget emits the following signals, besides the ones sent from GLView:

  • “focused” - when glview has received focus.
  • “unfocused” - when glview has lost focus.
  • “language,changed” - the program's language changed

This is how to register a callback. 

evas_object_smart_callback_add(glview, "focused", _focused_cb, data);
 
// Callback function for the "focused" signal
// This callback is called when the GLView is focused
static void
_focused_cb(void *data, Evas_Object *obj, void  *event_info)
{
   Elm_Focus_Info *fi = event_info;
   printf("GLView is focused\n");
}

A Glview Example

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