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Android) add mechanics to resume application from background #660

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Android) add mechanics to resume application from background #660

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99 changes: 89 additions & 10 deletions src/Magnum/Platform/AndroidApplication.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -120,15 +120,17 @@ bool AndroidApplication::tryCreate(const Configuration& configuration, const GLC
return false;
}

_glConfiguration = glConfiguration;

/* Choose config */
const EGLint configAttributes[] = {
EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
EGL_RED_SIZE, glConfiguration.colorBufferSize().r(),
EGL_GREEN_SIZE, glConfiguration.colorBufferSize().g(),
EGL_BLUE_SIZE, glConfiguration.colorBufferSize().b(),
EGL_ALPHA_SIZE, glConfiguration.colorBufferSize().a(),
EGL_DEPTH_SIZE, glConfiguration.depthBufferSize(),
EGL_STENCIL_SIZE, glConfiguration.stencilBufferSize(),
EGL_RED_SIZE, _glConfiguration.colorBufferSize().r(),
EGL_GREEN_SIZE, _glConfiguration.colorBufferSize().g(),
EGL_BLUE_SIZE, _glConfiguration.colorBufferSize().b(),
EGL_ALPHA_SIZE, _glConfiguration.colorBufferSize().a(),
EGL_DEPTH_SIZE, _glConfiguration.depthBufferSize(),
EGL_STENCIL_SIZE, _glConfiguration.stencilBufferSize(),
EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
EGL_NONE
};
Expand Down Expand Up @@ -176,6 +178,71 @@ bool AndroidApplication::tryCreate(const Configuration& configuration, const GLC
return _context->tryCreate(glConfiguration);
}

bool AndroidApplication::reactivateContext() {
/* Choose config */
const EGLint configAttributes[] = {
EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
EGL_RED_SIZE, _glConfiguration.colorBufferSize().r(),
EGL_GREEN_SIZE, _glConfiguration.colorBufferSize().g(),
EGL_BLUE_SIZE, _glConfiguration.colorBufferSize().b(),
EGL_ALPHA_SIZE, _glConfiguration.colorBufferSize().a(),
EGL_DEPTH_SIZE, _glConfiguration.depthBufferSize(),
EGL_STENCIL_SIZE, _glConfiguration.stencilBufferSize(),
EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
EGL_NONE
};
EGLint configCount;
EGLConfig config;
if (!eglChooseConfig(_display, configAttributes, &config, 1, &configCount)) {
Error() << "Platform::AndroidApplication::tryCreate(): cannot choose EGL config:"
<< Implementation::eglErrorString(eglGetError());
return false;
}

/* Resize native window and match it to the selected format */
EGLint format;
CORRADE_INTERNAL_ASSERT_OUTPUT(eglGetConfigAttrib(_display, config, EGL_NATIVE_VISUAL_ID, &format));
ANativeWindow_setBuffersGeometry(_state->window,
configuration.size().isZero() ? 0 : configuration.size().x(),
configuration.size().isZero() ? 0 : configuration.size().y(), format);

/* Create surface and context */
if (!(_surface = eglCreateWindowSurface(_display, config, _state->window, nullptr))) {
Error() << "Platform::AndroidApplication::tryCreate(): cannot create EGL window surface:"
<< Implementation::eglErrorString(eglGetError());
return false;
}

/* Make the context current */
CORRADE_INTERNAL_ASSERT_OUTPUT(eglMakeCurrent(_display, _surface, _surface, _glContext));
return true;
}

void AndroidApplication::pauseContext() {
/* Pause the context current */
CORRADE_INTERNAL_ASSERT_OUTPUT(eglMakeCurrent(_display, nullptr, nullptr, nullptr));
Comment on lines +222 to +223
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Would this work if you kept the context current and just made it bound to no surface at all?

Suggested change
/* Pause the context current */
CORRADE_INTERNAL_ASSERT_OUTPUT(eglMakeCurrent(_display, nullptr, nullptr, nullptr));
/* Keep the GL context current but without any surface */
CORRADE_INTERNAL_ASSERT_OUTPUT(eglMakeCurrent(_display, EGL_NO_SURFACE, EGL_NO_SURFACE, _glContext));

Because I'm wondering if it's guaranteed that no app code gets executed between APP_CMD_LOST_FOCUS and APP_CMD_INIT_WINDOW. And if it does, it'd be probably good to have the GL context current.

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The suggested change, at least from my side, seems to work fine.

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I'm wondering if it's guaranteed that no app code gets executed between APP_CMD_LOST_FOCUS and APP_CMD_INIT_WINDOW

I'm not sure about there being a guarantee, but it's one of the reasons I added _application_has_valid_surface - such that the user has some info to branch on.


_application_has_valid_surface = false;
}

void AndroidApplication::pauseApplication()
{
pauseContext();
}

void AndroidApplication::resumeApplication()
{
reactivateContext();
}

bool AndroidApplication::hasValidSurface() {
return _application_has_valid_surface;
}

bool AndroidApplication::hasFocus() {
return _application_has_focus;
}

Vector2i AndroidApplication::framebufferSize() const {
return {ANativeWindow_getWidth(_state->window),
ANativeWindow_getHeight(_state->window)};
Expand Down Expand Up @@ -214,18 +281,30 @@ void AndroidApplication::commandEvent(android_app* state, int32_t cmd) {
/* Create the application */
if(!data.instance) {
data.instance = data.instancer(state);
data.instance->drawEvent();
}
else {
data.instance->resumeApplication();
}
data.instance->drawEvent();
data.instance->_application_has_valid_surface = true;
break;

case APP_CMD_TERM_WINDOW:
/* Destroy the application */
data.instance.reset();
/* This can occur if: the application is destroyed, or just sent to the background */
if (data.instance) {
data.instance->pauseApplication();
}
break;

case APP_CMD_GAINED_FOCUS:
if (data.instance) {
data.instance->_application_has_focus = true;
}
break;
case APP_CMD_LOST_FOCUS:
/** @todo Make use of these */
if (data.instance) {
data.instance->_application_has_focus = false;
}
break;

case APP_CMD_CONFIG_CHANGED: {
Expand Down
50 changes: 50 additions & 0 deletions src/Magnum/Platform/AndroidApplication.h
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Original file line number Diff line number Diff line change
Expand Up @@ -346,6 +346,51 @@ class AndroidApplication {

/** @{ @name Screen handling */

/**
* @brief Recreate the OpenGL context
*
* returns @cpp false @ce if the context cannot be created,
* @cpp true @ce otherwise.
*/
bool reactivateContext();

/**
* @brief Pause the OpenGL context
*
*
*/
void pauseContext();

/**
* @brief Pause the Application
*
* Called when the application is attempted to be terminated or sent to the background
*/
virtual void pauseApplication();

/**
* @brief Resume the Application
*
* Called when the application comes back to the foreground
*/
virtual void resumeApplication();

/**
* @brief OpenGL surface useability
*
* returns @cpp false @ce if the surface is not available for rendering
* @cpp true @ce otherwise.
*/
bool hasValidSurface();

/**
* @brief Application focus
*
* returns @cpp false @ce if the application is not focused.
* @cpp true @ce otherwise.
*/
bool hasFocus();

public:
/**
* @brief Window size
Expand Down Expand Up @@ -564,6 +609,11 @@ class AndroidApplication {
EGLSurface _surface;
EGLContext _glContext;

GLConfiguration _glConfiguration;

bool _application_has_valid_surface = false;
bool _application_has_focus = false;

/* We have no way to query previous pointer positions, so we have to
maintain them like this. For pointers capable of hover (mouse, pen)
the _previousHoverPointerPosition is used, NaN signalling that the
Expand Down