android/android-emugl/host/libs/libOpenglRender/FbConfig.h

// Copyright (C) 2015 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef _LIBRENDER_FB_CONFIG_H
#define _LIBRENDER_FB_CONFIG_H

#include <EGL/egl.h>
#include <EGL/eglext.h>
#include <GLES/gl.h>

#include <stddef.h>

// A class used to model a guest EGL config.
// This really wraps a host EGLConfig handle, and provides a few cached
// attributes that can be retrieved through direct accessors, like
// getDepthSize().
//
// Each FbConfig is identified by a unique id which is its index in
// an FbConfigList instance (as declared below). It is not related to
// the host EGLConfig value or its EGL_CONFIG_ID.
//
// One doesn't create an FbConfig instance. Instead, create and initialize
// an FbConfigList from the host EGLDisplay, and use its size() and get()
// methods to access it.
class FbConfig {
public:
    // Destructor
    ~FbConfig();

    // Retrieve host EGLConfig.
    EGLConfig getEglConfig() const { return mEglConfig; }

    // Get depth size in bits.
    GLuint getDepthSize() const { return getAttribValue(0); }

    // Get stencil size in bits.
    GLuint getStencilSize() const { return getAttribValue(1); }

    // Get renderable type mask.
    GLuint getRenderableType() const { return getAttribValue(2); }

    // Get surface type mask.
    GLuint getSurfaceType() const { return getAttribValue(3); }

    // Get the EGL_CONFIG_ID value. This is the same as the one of the
    // underlying host EGLConfig handle.
    GLint getConfigId() const { return (GLint)getAttribValue(4); }

private:
    FbConfig();
    FbConfig(FbConfig& other);

    explicit FbConfig(EGLConfig hostConfig, EGLDisplay hostDisplay);

    friend class FbConfigList;

    GLuint getAttribValue(int n) const {
        return mAttribValues ? mAttribValues[n] : 0U;
    }

    EGLConfig mEglConfig;
    GLint* mAttribValues;
};

// A class to model the list of FbConfig for a given EGLDisplay, this is
// built from the list of host EGLConfig handles, filtered to only accept
// configs that are useful by the rendering library (e.g. they must support
// PBuffers and RGB pixel values).
//
// Usage is the following:
//
// 1) Create new instance by passing host EGLDisplay value.
//
// 2) Call empty() to check that the list is not empty, which would indicate
//    an error during creation.
//
// 3) FbConfig instances are identified by numbers in 0..(N-1) range, where
//    N is the result of the size() method.
//
// 4) Convert an FbConfig id into an FbConfig instance with get().
//
// 5) Use getPackInfo() and packConfigs() to retrieve information about
//    available configs to the guest.
class FbConfigList {
public:
    // Create a new list of FbConfig instance, by querying all compatible
    // host configs from |display|. A compatible config is one that supports
    // Pbuffers and RGB pixel values.
    //
    // After construction, call empty() to check if there are items.
    // An empty list means there was an error during construction.
    explicit FbConfigList(EGLDisplay display);

    // Destructor.
    ~FbConfigList();

    // Return true iff the list is empty. true means there was an error
    // during construction.
    bool empty() const { return mCount == 0; }

    // Return the number of FbConfig instances in the list.
    // Each instance is identified by a number from 0 to N-1,
    // where N is the result of this function.
    size_t size() const { return static_cast<size_t>(mCount); }

    // Retrieve the FbConfig instance associated with |guestId|,
    // which must be an integer between 0 and |size() - 1|. Returns
    // NULL in case of failure.
    const FbConfig* get(int guestId) const {
        if (guestId >= 0 && guestId < mCount) {
            return mConfigs[guestId];
        } else {
            return NULL;
        }
    }

    // Use |attribs| a list of EGL attribute name/values terminated by
    // EGL_NONE, to select a set of matching FbConfig instances.
    //
    // On success, returns the number of matching instances.
    // If |configs| is not NULL, it will be populated with the guest IDs
    // of the matched FbConfig instances.
    //
    // |configsSize| is the number of entries in the |configs| array. The
    // function will never write more than |configsSize| entries into
    // |configsSize|.
    EGLint chooseConfig(const EGLint* attribs,
                        EGLint* configs,
                        EGLint configsSize) const;

    // Retrieve information that can be sent to the guest before packed
    // config list information. If |numConfigs| is NULL, then |*numConfigs|
    // will be set on return to the number of config instances.
    // If |numAttribs| is not NULL, then |*numAttribs| will be set on return
    // to the number of attribute values cached by each FbConfig instance.
    void getPackInfo(EGLint* mumConfigs, EGLint* numAttribs) const;

    // Write the full list information into an array of EGLuint items.
    // |buffer| is the output buffer that will receive the data.
    // |bufferByteSize| is teh buffer size in bytes.
    // On success, this returns
    EGLint packConfigs(GLuint bufferByteSize, GLuint* buffer) const;

private:
    FbConfigList(const FbConfigList& other) = delete;

    int mCount = 0;
    FbConfig** mConfigs = nullptr;
    EGLDisplay mDisplay = 0;
};

#endif  // _LIBRENDER_FB_CONFIG_H