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impeller::egl::Display Class Reference

A connection to an EGL display. Only one connection per application instance is sufficient. More...

`#include <display.h>`

## Public Member Functions
| Display ()
virtual | ~Display ()
virtual bool | IsValid () const
virtual std::unique_ptr< Config > | ChooseConfig (ConfigDescriptor config) const
| Choose a config that most closely matches a given descriptor. If there are no matches, this method returns `nullptr`. More...
virtual std::unique_ptr< Context > | CreateContext (const Config &config, const Context *share_context)
| Create a context with a supported config. The supported config can be obtained via a successful call to `ChooseConfig`. More...
virtual std::unique_ptr< Surface > | CreateWindowSurface (const Config &config, EGLNativeWindowType window)
| Create a window surface. The window is an opaque pointer whose value value is platform specific. For instance, ANativeWindow on Android. More...
virtual std::unique_ptr< Surface > | CreatePixelBufferSurface (const Config &config, size_t width, size_t height)
| Create an offscreen pixelbuffer surface. These are of limited use except in the context where applications need to render to a texture in an offscreen context. In such cases, a 1x1 pixel buffer surface is created to obtain a surface that can be used to make the context current on the background thread. More...

## Detailed Description

A connection to an EGL display. Only one connection per application instance is sufficient.

The display connection is used to first choose a config from among the available, create a context from that config, and then use that context with a surface on one (and only one) thread at a time.

Definition at line 28 of file display.h.

## Constructor & Destructor Documentation

## ◆ Display()

impeller::egl::Display::Display | ( |  | ) |

Definition at line 15 of file display.cc.

15 {
16 EGLDisplay display = eglGetDisplay(EGL_DEFAULT_DISPLAY);
17
18 if (::eglInitialize(display, nullptr, nullptr) != EGL_TRUE) {
19 IMPELLER_LOG_EGL_ERROR;
20 return;
21 }
22 display_ = display;
23 }

References IMPELLER_LOG_EGL_ERROR.

## ◆ ~Display()

impeller::egl::Display::~Display | ( |  | ) |
| virtual

Definition at line 25 of file display.cc.

25 {
26 if (display_ != EGL_NO_DISPLAY) {
27 if (::eglTerminate(display_) != EGL_TRUE) {
28 IMPELLER_LOG_EGL_ERROR;
29 }
30 }
31 }

References IMPELLER_LOG_EGL_ERROR.

## Member Function Documentation

## ◆ ChooseConfig()

std::unique_ptr< Config > impeller::egl::Display::ChooseConfig | ( | ConfigDescriptor | config | ) | const
| virtual

Choose a config that most closely matches a given descriptor. If there are no matches, this method returns `nullptr`.

Parameters

  [in] | config | The configuration

Returns
  A config that matches a descriptor if one is available. `nullptr` otherwise.

Definition at line 72 of file display.cc.

72 {
73 if (!display_) {
74 return nullptr;
75 }
76
77 std::vector<EGLint> attributes;
78
79 {
80 attributes.push_back(EGL_RENDERABLE_TYPE);
81 switch (config.api) {
82 case API::kOpenGL:
83 attributes.push_back(EGL_OPENGL_BIT);
84 break;
85 case API::kOpenGLES2:
86 attributes.push_back(EGL_OPENGL_ES2_BIT);
87 break;
88 case API::kOpenGLES3:
89 attributes.push_back(EGL_OPENGL_ES3_BIT);
90 break;
91 }
92 }
93
94 {
95 attributes.push_back(EGL_SURFACE_TYPE);
96 switch (config.surface_type) {
97 case SurfaceType::kWindow:
98 attributes.push_back(EGL_WINDOW_BIT);
99 break;
100 case SurfaceType::kPBuffer:
101 attributes.push_back(EGL_PBUFFER_BIT);
102 break;
103 }
104 }
105
106 {
107 switch (config.color_format) {
108 case ColorFormat::kRGBA8888:
109 attributes.push_back(EGL_RED_SIZE);
110 attributes.push_back(8);
111 attributes.push_back(EGL_GREEN_SIZE);
112 attributes.push_back(8);
113 attributes.push_back(EGL_BLUE_SIZE);
114 attributes.push_back(8);
115 attributes.push_back(EGL_ALPHA_SIZE);
116 attributes.push_back(8);
117 break;
118 case ColorFormat::kRGB565:
119 attributes.push_back(EGL_RED_SIZE);
120 attributes.push_back(5);
121 attributes.push_back(EGL_GREEN_SIZE);
122 attributes.push_back(6);
123 attributes.push_back(EGL_BLUE_SIZE);
124 attributes.push_back(5);
125 break;
126 }
127 }
128
129 {
130 attributes.push_back(EGL_DEPTH_SIZE);
131 attributes.push_back(static_cast<EGLint>(config.depth_bits));
132 }
133
134 {
135 attributes.push_back(EGL_STENCIL_SIZE);
136 attributes.push_back(static_cast<EGLint>(config.stencil_bits));
137 }
138
139 {
140 const auto sample_count = static_cast<EGLint>(config.samples);
141 if (sample_count > 1) {
142 attributes.push_back(EGL_SAMPLE_BUFFERS);
143 attributes.push_back(1);
144 attributes.push_back(EGL_SAMPLES);
145 attributes.push_back(sample_count);
146 }
147 }
148
149 // termination sentinel must be present.
150 attributes.push_back(EGL_NONE);
151
152 EGLConfig config_out = nullptr;
153 EGLint config_count_out = 0;
154 if (::eglChooseConfig(display_, // display
155 attributes.data(), // attributes (null terminated)
156 &config_out, // matched configs
157 1, // configs array size
158 &config_count_out // match configs count
159 ) != EGL_TRUE) {
160 IMPELLER_LOG_EGL_ERROR;
161 return nullptr;
162 }
163
164 if (config_count_out != 1u) {
165 IMPELLER_LOG_EGL_ERROR;
166 return nullptr;
167 }
168
169 return std::make_unique<Config>(config, config_out);
170 }

References impeller::egl::ConfigDescriptor::api, impeller::egl::ConfigDescriptor::color_format, impeller::egl::ConfigDescriptor::depth_bits, IMPELLER_LOG_EGL_ERROR, impeller::egl::kOpenGL, impeller::egl::kOpenGLES2, impeller::egl::kOpenGLES3, impeller::egl::kPBuffer, impeller::egl::kRGB565, impeller::egl::kRGBA8888, impeller::egl::kWindow, impeller::egl::ConfigDescriptor::samples, impeller::egl::ConfigDescriptor::stencil_bits, and impeller::egl::ConfigDescriptor::surface_type.

## ◆ CreateContext()

std::unique_ptr< Context > impeller::egl::Display::CreateContext | ( | const Config & | config,
|  | const Context * | share_context
| ) |  |
| virtual

Create a context with a supported config. The supported config can be obtained via a successful call to `ChooseConfig`.

Parameters

  [in] | config | The configuration.
  [in] | share_context | The share context. Context within the same share-group use the same handle table. The contexts should still only be used exclusively on each thread however.

Returns
  A context if one can be created. `nullptr` otherwise.

Definition at line 37 of file display.cc.

38 {
39 const auto& desc = config.GetDescriptor();
40
41 std::vector<EGLint> attributes;
42 switch (desc.api) {
43 case API::kOpenGL:
44 break;
45 case API::kOpenGLES2:
46 attributes.push_back(EGL_CONTEXT_CLIENT_VERSION);
47 attributes.push_back(2);
48 break;
49 case API::kOpenGLES3:
50 attributes.push_back(EGL_CONTEXT_CLIENT_VERSION);
51 attributes.push_back(3);
52 break;
53 }
54 // Termination sentinel must be present.
55 attributes.push_back(EGL_NONE);
56
57 auto context = ::eglCreateContext(
58 display_, // display
59 config.GetHandle(), // config
60 share_context != nullptr ? share_context->GetHandle() : nullptr, // share
61 attributes.data() // attributes
62 );
63
64 if (context == EGL_NO_CONTEXT) {
65 IMPELLER_LOG_EGL_ERROR;
66 return nullptr;
67 }
68
69 return std::unique_ptr<Context>(new Context(display_, context));
70 }

References impeller::egl::Config::GetDescriptor(), impeller::egl::Context::GetHandle(), impeller::egl::Config::GetHandle(), IMPELLER_LOG_EGL_ERROR, impeller::egl::kOpenGL, impeller::egl::kOpenGLES2, and impeller::egl::kOpenGLES3.

## ◆ CreatePixelBufferSurface()

std::unique_ptr< Surface > impeller::egl::Display::CreatePixelBufferSurface | ( | const Config & | config,
|  | size_t | width,
|  | size_t | height
| ) |  |
| virtual

Create an offscreen pixelbuffer surface. These are of limited use except in the context where applications need to render to a texture in an offscreen context. In such cases, a 1x1 pixel buffer surface is created to obtain a surface that can be used to make the context current on the background thread.

Parameters

  [in] | config | The configuration
  [in] | width | The width
  [in] | height | The height

Returns
  A valid pixel buffer surface if one can be created. `nullptr` otherwise.

Definition at line 188 of file display.cc.

190 {
191 // clang-format off
192 const EGLint attribs[] = {
193 EGL_WIDTH, static_cast<EGLint>(width),
194 EGL_HEIGHT, static_cast<EGLint>(height),
195 EGL_NONE
196 };
197 // clang-format on
198 auto surface = ::eglCreatePbufferSurface(display_, // display
199 config.GetHandle(), // config
200 attribs // attrib_list
201 );
202 if (surface == EGL_NO_SURFACE) {
203 IMPELLER_LOG_EGL_ERROR;
204 return nullptr;
205 }
206 return std::unique_ptr<Surface>(new Surface(display_, surface));
207 }

References impeller::egl::Config::GetHandle(), and IMPELLER_LOG_EGL_ERROR.

## ◆ CreateWindowSurface()

std::unique_ptr< Surface > impeller::egl::Display::CreateWindowSurface | ( | const Config & | config,
|  | EGLNativeWindowType | window
| ) |  |
| virtual

Create a window surface. The window is an opaque pointer whose value value is platform specific. For instance, ANativeWindow on Android.

Parameters

  [in] | config | A valid configuration. One can be obtained via `ChooseConfig`.
  [in] | window | An opaque pointer to a platform specific window handle.

Returns
  A valid window surface if one can be created. `nullptr` otherwise.

Definition at line 172 of file display.cc.

174 {
175 const EGLint attribs[] = {EGL_NONE};
176 auto surface = ::eglCreateWindowSurface(display_, // display
177 config.GetHandle(), // config
178 window, // window
179 attribs // attrib_list
180 );
181 if (surface == EGL_NO_SURFACE) {
182 IMPELLER_LOG_EGL_ERROR;
183 return nullptr;
184 }
185 return std::unique_ptr<Surface>(new Surface(display_, surface));
186 }

References impeller::egl::Config::GetHandle(), and IMPELLER_LOG_EGL_ERROR.

## ◆ IsValid()

bool impeller::egl::Display::IsValid | ( |  | ) | const
| virtual

Returns
  True if the display connection is valid.

Definition at line 33 of file display.cc.

33 {
34 return display_ != EGL_NO_DISPLAY;
35 }

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

- impeller/toolkit/egl/display.h
- impeller/toolkit/egl/display.cc

impeller::egl::ColorFormat::kRGB565
@ kRGB565
impeller::egl::API::kOpenGLES2
@ kOpenGLES2
impeller::egl::API::kOpenGL
@ kOpenGL
impeller::egl::SurfaceType::kWindow
@ kWindow
IMPELLER_LOG_EGL_ERROR
#define IMPELLER_LOG_EGL_ERROR
Definition: egl.h:25
impeller::egl::ColorFormat::kRGBA8888
@ kRGBA8888
impeller::egl::API::kOpenGLES3
@ kOpenGLES3
impeller::egl::SurfaceType::kPBuffer
@ kPBuffer