Karma::KarmaGuiOpenGLHandler Class Reference

The chief class for KarmaGui's OpenGL based backend renderer. More...

#include <KarmaGuiOpenGLHandler.h>

Static Public Member Functions
static bool	KarmaGui_ImplOpenGL3_Init (const char *glsl_version=NULL)
	Initializing OpenGL backend renderer.
static void	KarmaGui_ImplOpenGL3_InitPlatformInterface ()
	KarmaGuiPlatformIO 's instance's member, platform_io.Renderer_RenderWindow, is set to KarmaGui_ImplOpenGL3_RenderWindow.
static void	KarmaGui_ImplOpenGL3_ShutdownPlatformInterface ()
	Destroy window(s) opened in viewport(s) and clear the data.
static void	KarmaGui_ImplOpenGL3_Shutdown ()
	Function called when KarmaGui layer shuts down (happens when LayerStack is destroyed). Call stack is like so: KarmaGuiLayer::OnDetach() -> KarmaGuiRenderer::OnKarmaGuiLayerDetach() -> KarmaGuiOpenGLHandler::KarmaGui_ImplOpenGL3_Shutdown().
static void	KarmaGui_ImplOpenGL3_NewFrame ()
	Function called in the begining of each KarmaGui's render loop.
static void	KarmaGui_ImplOpenGL3_RenderDrawData (KGDrawData *draw_data)
	The routine for rendering the Karma's UI using OpenGL3 API.
static void	KarmaGui_ImplOpenGL3_SetupRenderState (KGDrawData *draw_data, int fb_width, int fb_height, GLuint vertex_array_object)
	Setup render state: alpha-blending (process of combining one image with a background to create the appearance of partial or full transparency) enabled, no face culling, no depth testing, scissor enabled, polygon fill, setup viewport. Bind vertex/index buffers and setup attributes for KGDrawVert.
static bool	CheckShader (GLuint handle, const char *desc)
	A check for success of shader (within KarmaGuiOpenGLHandler context) compilation.
static bool	CheckProgram (GLuint handle, const char *desc)
	A check for the success of shader (within KarmaGuiOpenGLHandler context) linking.
static void	KarmaGui_ImplOpenGL3_RenderWindow (KarmaGuiViewport *viewport, void *render_arg)
	Prepares the context for OpenGl's rendering of KarmaGui's primitives and calls the function KarmaGui_ImplOpenGL3_RenderDrawData.
static void	KarmaGui_ImplOpenGL3_CreateTexture (char const *fileName, const std::string &label="")
	A helper function to generate texture, in appropriate format, and add to the list openglMesaDecalDataList for use.
static bool	KarmaGui_ImplOpenGL3_CreateFontsTexture ()
	A function to generate texture for OpenGL fonts The following steps are taken:
static void	KarmaGui_ImplOpenGL3_DestroyFontsTexture ()
	Clear up the resources occupied by the fonts and decals, all the textures in this context.
static bool	KarmaGui_ImplOpenGL3_CreateDeviceObjects ()
	Creates and generates shaders and buffers to be used along with the necessary uniforms.
static void	KarmaGui_ImplOpenGL3_DestroyDeviceObjects ()
	Clears up all the resources (shaders, buffers, and uniforms) allocated in KarmaGui_ImplOpenGL3_CreateDeviceObjects()

Detailed Description

The chief class for KarmaGui's OpenGL based backend renderer.

Since

Karma 1.0.0

Member Function Documentation

CheckProgram()

bool Karma::KarmaGuiOpenGLHandler::CheckProgram ( GLuint handle, const char * desc )

static

A check for the success of shader (within KarmaGuiOpenGLHandler context) linking.

The following log message is printed on the occurance of the linking error detected by the check

[03:36:56][error] KARMA: KarmaGuiOpenGLHandler::CheckProgram: failed to link shader program! With GLSL:#version 410
[03:36:56][error] KARMA: ERROR: One or more attached shaders not successfully compiled

Parameters

handle	The GL program (for shader object) object being queried
desc	The category name of the program object. For instance "shader program" (only)

Since

Karma 1.0.0

CheckShader()

bool Karma::KarmaGuiOpenGLHandler::CheckShader ( GLuint handle, const char * desc )

static

A check for success of shader (within KarmaGuiOpenGLHandler context) compilation.

The following log message is printed on the occurance of compilation error detected by the check

[03:06:44][error] KARMA: KarmaGuiOpenGLHandler::CheckShader: failed to compile vertex shader! With GLSL:#version 410
[03:06:49][error] KARMA: ERROR: 0:3: 'layout' : syntax error: syntax error

Parameters

handle	The shader object being queried
desc	The category name of the shader object. For instance "vertex shader" or "fragment shader"

Since

Karma 1.0.0

KarmaGui_ImplOpenGL3_CreateDeviceObjects()

bool Karma::KarmaGuiOpenGLHandler::KarmaGui_ImplOpenGL3_CreateDeviceObjects ( )

static

Creates and generates shaders and buffers to be used along with the necessary uniforms.

Since

Karma 1.0.0

KarmaGui_ImplOpenGL3_CreateFontsTexture()

bool Karma::KarmaGuiOpenGLHandler::KarmaGui_ImplOpenGL3_CreateFontsTexture ( )

static

A function to generate texture for OpenGL fonts The following steps are taken:

1. Texture atlas is built from KGFontAtlas. This is done by first loading the font atlas in the form RGBA 32-bit (with 75% wastage). Then the creation of a 2D texture (GL_TEXTURE_2D), with appropriate name(s), by glGenTextures -> glBindTexture -> glTexImage2D -> target texture (or atlas)
2. Finally the target texture is stored like so; io.Fonts->SetTexID

Since

Karma 1.0.0

KarmaGui_ImplOpenGL3_CreateTexture()

void Karma::KarmaGuiOpenGLHandler::KarmaGui_ImplOpenGL3_CreateTexture ( char const * fileName, const std::string & label = "" )

static

A helper function to generate texture, in appropriate format, and add to the list openglMesaDecalDataList for use.

Parameters

fileName	The path to the file containing texture
label	The name of the texture for identification purpose

See also

OpenGLImageBuffer::SetUpImageBuffer

Since

Karma 1.0.0

KarmaGui_ImplOpenGL3_DestroyDeviceObjects()

void Karma::KarmaGuiOpenGLHandler::KarmaGui_ImplOpenGL3_DestroyDeviceObjects ( )

static

Clears up all the resources (shaders, buffers, and uniforms) allocated in KarmaGui_ImplOpenGL3_CreateDeviceObjects()

Since

Karma 1.0.0

KarmaGui_ImplOpenGL3_DestroyFontsTexture()

void Karma::KarmaGuiOpenGLHandler::KarmaGui_ImplOpenGL3_DestroyFontsTexture ( )

static

Clear up the resources occupied by the fonts and decals, all the textures in this context.

Since

Karma 1.0.0

KarmaGui_ImplOpenGL3_Init()

bool Karma::KarmaGuiOpenGLHandler::KarmaGui_ImplOpenGL3_Init ( const char * glsl_version = NULL )

static

Initializing OpenGL backend renderer.

The following steps are taken:

1. KarmaGuiContext's members, chiefly BackendRendererUserData and flags, are set
2. Based on KGGuiConfigFlags_ViewportsEnable, drag and drop feature is set up by calling KarmaGui_ImplOpenGL3_InitPlatformInterface()

Parameters

glsl_version

The version of OpenGL driver being used

Since

Karma 1.0.0

KarmaGui_ImplOpenGL3_InitPlatformInterface()

void Karma::KarmaGuiOpenGLHandler::KarmaGui_ImplOpenGL3_InitPlatformInterface ( )

static

KarmaGuiPlatformIO 's instance's member, platform_io.Renderer_RenderWindow, is set to KarmaGui_ImplOpenGL3_RenderWindow.

Note

There is one global instance of KarmaGuiPlatformIO, in this context, which can be retrieved by KarmaGui::GetPlatformIO (basically GKarmaGui->PlatformIO)

Since

Karma 1.0.0

KarmaGui_ImplOpenGL3_NewFrame()

void Karma::KarmaGuiOpenGLHandler::KarmaGui_ImplOpenGL3_NewFrame ( )

static

Function called in the begining of each KarmaGui's render loop.

In minor detail, the sequence is like so

1. Application::Run
2. m_KarmaGuiLayer->Begin() -> KarmaGuiRenderer::OnKarmaGuiLayerBegin() -> KarmaGui_ImplOpenGL3_NewFrame()
3. each layer->KarmaGuiRender(deltaTime);
4. m_KarmaGuiLayer->End();

Note

Should be called after ImGui_ImplOpenGL3_Init() because BackendRendererUserData (io.BackendRendererUserData) must be already instantiated and initialized.

Since

Karma 1.0.0

KarmaGui_ImplOpenGL3_RenderDrawData()

void Karma::KarmaGuiOpenGLHandler::KarmaGui_ImplOpenGL3_RenderDrawData ( KGDrawData * draw_data )

static

The routine for rendering the Karma's UI using OpenGL3 API.

Basically all that is drawn for Karma's UI (and inside the UI, including text, textures, and all that) is nothing but the set of triangles (KGDrawList). The relevant information is written in KGDrawData instance by the call Karma::KarmaGui::Render()

Parameters

draw_data

The data to render a KarmaGui frame

Note

We use ocornut's callback technique https://github.com/ocornut/imgui/issues/475#issuecomment-169953139 to render 3d scene inside KarmaGui's UI element

See also

KarmaGui_ImplOpenGL3_SetupRenderState()

Since

Karma 1.0.0

KarmaGui_ImplOpenGL3_RenderWindow()

void Karma::KarmaGuiOpenGLHandler::KarmaGui_ImplOpenGL3_RenderWindow ( KarmaGuiViewport * viewport, void * render_arg )

static

Prepares the context for OpenGl's rendering of KarmaGui's primitives and calls the function KarmaGui_ImplOpenGL3_RenderDrawData.

Note

This function is supplied to KarmaGuiPlatformIO's Renderer_RenderWindow member and then KarmaGuiRenderer (via call in KarmaGuiRenderer::OnKarmaGuiLayerEnd()) takes care of the rest of rendering sequence. This is done for incorporating even the helper modular design.

Parameters

viewport	The only single platform window since we are not working with multi-viewport
render_arg	Is the value passed to KarmaGui::RenderPlatformWindowsDefault() by KarmaGuiRenderer::OnKarmaGuiLayerEnd(), usually NULL

Since

Karma 1.0.0

KarmaGui_ImplOpenGL3_SetupRenderState()

void Karma::KarmaGuiOpenGLHandler::KarmaGui_ImplOpenGL3_SetupRenderState ( KGDrawData * draw_data, int fb_width, int fb_height, GLuint vertex_array_object )

static

Setup render state: alpha-blending (process of combining one image with a background to create the appearance of partial or full transparency) enabled, no face culling, no depth testing, scissor enabled, polygon fill, setup viewport. Bind vertex/index buffers and setup attributes for KGDrawVert.

Parameters

draw_data	The collection of variables composing the draw data to render a KarmaGui frame
fb_width	The width of the KarmaGui's rendering scope (draw_data->DisplaySize.x * draw_data->FramebufferScale.x), for glViewport's use.
fb_height	The height of the KarmaGui's rendering scope (draw_data->DisplaySize.y * draw_data->FramebufferScale.y), for glViewport's use.
vertex_array_object	The name of the OpenGl vertexarray object

Todo

An amature work: try using math GLM's projection matrix for orthographic view

Since

Karma 1.0.0

KarmaGui_ImplOpenGL3_Shutdown()

void Karma::KarmaGuiOpenGLHandler::KarmaGui_ImplOpenGL3_Shutdown ( )

static

Function called when KarmaGui layer shuts down (happens when LayerStack is destroyed). Call stack is like so: KarmaGuiLayer::OnDetach() -> KarmaGuiRenderer::OnKarmaGuiLayerDetach() -> KarmaGuiOpenGLHandler::KarmaGui_ImplOpenGL3_Shutdown().

Since

Karma 1.0.0

KarmaGui_ImplOpenGL3_ShutdownPlatformInterface()

void Karma::KarmaGuiOpenGLHandler::KarmaGui_ImplOpenGL3_ShutdownPlatformInterface ( )

static

Destroy window(s) opened in viewport(s) and clear the data.

Note

The job of backend here is to clear the data (that may have got stored in e.g. PlatformUserData, RendererUserData) by self before KarmaGui clears in a systematic way

Todo

KarmaGuiOpenGLHandler seems to be not doing the right form of cleaning of resources because Renderer_Destroy_Window is not set like that in KarmaGuiVulkanHandler. Try to find a way.

Since

Karma 1.0.0

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The documentation for this class was generated from the following files:

• Karma/src/Platform/OpenGL/KarmaGuiOpenGLHandler.h
• Karma/src/Platform/OpenGL/KarmaGuiOpenGLHandler.cpp