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Update README.md with tiny code samples on how to use the new C++ objects

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Markus Tavenrath 2016-02-23 19:26:28 +01:00
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@ -143,33 +143,32 @@ vk::createImage(device, &ci, allocator, &image));
# Enhancements beyond the API
While mapping the Vulkan API to C++ without adding new functions is already a big help, one can do even more by adding new functionality. For example several C++ developers tend to use std::string and std::vector in their code, therefore we have added some more optional convenience features:
* Use <code>std::string</code> instead of <code>const char *</code> for strings
* Use <code>std::vector</code> instead of <code>(count, ptr)</code> for sized arrays
* Throw exceptions instead of error return values (in progress)
* Return handles/vectors where applicable, i.e. for the create* functions
As example let's examine the device extension property enumeration in Vulkan:
To provide a more object oriented feeling we're providing classes for each handle which include all Vulkan functions where the first
parameter matches the handle. In addition to this we made a few changes to the signatures of the member functions
* <code>(count, T*)</code> has been replaced by <code>std::vector&lt;T&gt;</code>
* <code>const char *</code> has been replaced by <std::string>
* vk::Result return values have been replaced by exceptions.
* Functions with a single output value do return this value instead
Here are a few code examples:
<pre>
<code>
uint32_t count;
VK_VERIFY(vk::enumerateDeviceExtensionProperties(physicalDevice, layerName.c_str(), &count, nullptr));
try {
vk::Instance i = ...;
std::vector<vk::PhysicalDevice> physicalDevices = i.enumeratePhysicalDevices();
vk::FormatProperties formatProperties = physicalDevices[0].getFormatProperties(vk::Format::eR8G8B8A8Unorm);
std::vector<vk::ExtensionProperties> properties(count);
VK_VERIFY(vk::enumerateDeviceExtensionProperties(physicalDevice, layerName.c_str(), &count, properties.data()));
vk::CommandBuffer commandBuffer = ...;
vk::Buffer buffer = ...;
commandBuffer.updateBuffer(buffer, 0, {some values}); // update buffer with std::vector
}
catch (vk::Exception e)
{
std::cerr << "Vulkan failure: " << e.what() << std::endl;
}
</code>
</pre>
Luckily the official Khronos-provided vk.xml has enough information to figure out which pair of values represents a sized array or strings, so that it is possible to generate a function which allows you to write the following line of code instead:
<pre>
<code>
std::vector&lt;ExtensionProperties&gt; properties = vk::enumerateDeviceExtensionProperties(physicalDevice, layerName);
</code>
</pre>
# Usage
To start with the C++ version of the Vulkan API download header from GIT, put it in a vulkan subdirectory and add
<code>#include &lt;vulkan/vk_cpp.h&gt;</code> to your source code.
@ -195,3 +194,14 @@ before this line:
* Update submodules: git submodule update --init --recursive
* Use CMake to generate a solution or makefile for your favourite build environment
* Launch the build
# Providing Pull Requests
NVIDIA is happy to review and consider pull requests for merging into the main tree of vkcpp for bug fixes and features. Before providing a pull request to NVIDIA, please note the following:
* A pull request provided to this repo by a developer constitutes permission from the developer for NVIDIA to merge the provided
changes or any NVIDIA modified version of these changes to the repo. NVIDIA may remove or change the code at any time and in any
way deemed appropriate. Due to the required paperwork please refrain from providing pull requests for simple changes and file an issue
describing a bug or the desired change instead.
* Not all pull requests can be or will be accepted. NVIDIA will close pull requests that it does not intend to merge.
* The modified files and any new files must include the unmodified NVIDIA copyright header seen at the top of all shipping files.