I want to use Camera(CameraCaptureUI or MediaCapture class) in C++/WinRT.
Microsoft document sample code is written by C# and JavaScript.
https://learn.microsoft.com/en-us/uwp/api/Windows.Media.Capture.CameraCaptureUI#code-snippet-1
MFC + C++/WinRT
void CWinRTtestDlg::OnBnClickedButtonToast()
{
// show toast
auto notificationManager = ToastNotificationManager::GetDefault();
auto toastXml = ToastNotificationManager::GetTemplateContent(ToastTemplateType::ToastText01);
auto textNode = toastXml.GetElementsByTagName(L"text").Item(0);
textNode.AppendChild(toastXml.CreateTextNode(L"Hello C++/WinRT!"));
auto toast = ToastNotification(toastXml);
toast.ExpirationTime(winrt::clock::now() + std::chrono::hours() * 2);
notificationManager.CreateToastNotifier().Show(toast);
}
this code is working.
IAsyncAction Camera()
{
auto cameraManager = CameraCaptureUI();
cameraManager.PhotoSettings().CroppedAspectRatio(Size(4, 3));
cameraManager.PhotoSettings().Format(CameraCaptureUIPhotoFormat::Jpeg);
auto file{ co_await cameraManager.CaptureFileAsync(CameraCaptureUIMode::Photo) };
}
void CWinRTtestDlg::OnBnClickedButtonCamera()
{
winrt::init_apartment();
auto image = Camera();
}
but this code is NOT working...
C++ project setting
Additional Option /await
C++ Language Standard C++17
Conformance mode No
Teams are slowly adding C++ samples, but it's going to take time. For the most part, a transliteration shouldn't be too hard. If it's a C# constructor, replace it with a C++ constructor. For example:
Widget widget = new Widget(123);
Becomes:
Widget widget(123);
Properties don't exist in C++ so you can just add parentheses and treat it as a method. You can also use coroutines, so an await in C# becomes a co_await in C++.
Related
RANT-BEGIN
Before jumping right into already answered band wagon, please read this paper about SE outdated answers https://ieeexplore.ieee.org/document/8669958
Things changes after a time, and I am afraid Computer science is one of the most if not the most field out there where APIs and Interfaces change radically very very fast. Needless to say that a solution that might worked last month might not after latest feature added to a platform/framework. I humbly request you to not mark this question as answered with decade old post when many mainstream things did not even existed. If you dont know latest solution dont bother about it and leave question for someone else who might.
For a community representative of Computer Science where innovations is everyday thing, it is very toxic, new comer unfriendly and conservative.
END-RANT
This question has already been answered by me and will be accepted tomorrow (SE policy). Thank you for your interest.
Many times you have function pointers in unmanaged context which are called by some kind of events, We will see how it can be achieved with Top-Level Functions and also with member functions of a managed class.
Again, Please dont mark it as answered by linking to a decade old posts.
PS:
So many edits due to unstable internet in third world country, yeah bite me!
unmanaged.cpp
#pragma unmanaged
// Declare an unmanaged function type that takes one int arguments and callbacks
// our function after incrementing it by 1
// Note the use of __stdcall for compatibility with managed code
// if your unmanaged callback uses any other calling convention you can
// UnmanagedFunctionPointerAttribute (check msdn for more info) on your delegate
typedef int(__stdcall* ANSWERCB)(int);//Signature of native callback
int TakesCallback(ANSWERCB fp, int a) {
if (fp) {
return fp(a+1);//Native Callback
}
// This code will be executed when passed without fp
return 0;
}
#pragma managed
managed.cpp
using namespace System;
using namespace System::Runtime::InteropServices;
namespace Callbacks {
// Following delegate is for unmanaged code and must match its signature
public delegate void MyNativeDelegate(int i);
// This delegate is for managed/derived code and ideally should have only managed parameters
public delegate void MyManagedDelegate(int i);
public ref class TestCallback {// Our demo Managed class
private:
GCHandle gch;// kept reference so that it can be freed once we are done with it
void NativeCallbackListener(int i);//unmanaged code will call this function
public:
void TriggerCallback(int i); // Its here for demo purposes, usually unmanaged code will call automatically
event MyManagedDelegate^ SomethingHappened;//plain old event
~TestCallback();//free gch in destructor as its managed.
};
};
void Callbacks::TestCallback::NativeCallbackListener(int i) {
// Callback from Native code,
// If you need to transform your arguments do it here, like transforming void* to somekind of native structure.
// and then pass SomethingHappened::raise with Managed Class/Struct
return SomethingHappened::raise(i); // similar to SomethingHappened.Invoke() in c#
}
void Callbacks::TestCallback::TriggerCallback(int i)
{
MyNativeDelegate^ fp = gcnew MyNativeDelegate(this, &TestCallback::NativeCallbackListener);
// use this if your nativecallback function is not a member function MyNativeDelegate^ fp = gcnew MyNativeDelegate(&NativeCallbackListener);
gch = GCHandle::Alloc(fp);
IntPtr ip = Marshal::GetFunctionPointerForDelegate(fp);
ANSWERCB cb = static_cast<ANSWERCB>(ip.ToPointer());// (ANSWERCB)ip.ToPointer(); works aswell
// Simulating native call, it should callback to our function ptr NativeCallbackListener with 2+1;
// Ideally Native code keeps function pointer and calls back without pointer being provided every time.
// Most likely with a dedicated function for that.
TakesCallback(cb, i);
}
void Callbacks::TestCallback::~TestCallBack() {
gch.Free();//Free GCHandle so GC can collect
}
implementation.cpp
using namespace System;
void OnSomethingHappened(int i);
int main(array<System::String^>^ args)
{
auto cb = gcnew Callbacks::TestCallback();
cb->SomethingHappened += gcnew Callbacks::MyManagedDelegate(&OnSomethingHappened);
cb->TriggerCallback(1);
return 0;
}
void OnSomethingHappened(int i)
{
Console::WriteLine("Got call back with " + i);
}
I'm not sure what I'm doing wrong, but even though I'm definitely on the UI thread, I'm consistently getting the error " 'The application called an interface that was marshalled for a different thread.'" when constructing Xaml controls in C++.
See the following basic example, which uses a stripped down version of the default C++/WinRT CoreApplication template:
#include "pch.h"
using namespace winrt;
using namespace Windows;
using namespace Windows::ApplicationModel::Core;
using namespace Windows::Foundation::Numerics;
using namespace Windows::UI;
using namespace Windows::UI::Core;
using namespace Windows::UI::Composition;
using namespace Windows::ApplicationModel::Activation;
struct App : implements<App, IFrameworkViewSource, IFrameworkView> {
CompositionTarget m_target{nullptr};
IFrameworkView CreateView() { return *this; }
void Initialize(CoreApplicationView const &) {}
void Load(hstring const &) {}
void Uninitialize() {}
void Run() {
CoreWindow window = CoreWindow::GetForCurrentThread();
winrt::Windows::UI::Xaml::Controls::TextBox textbox; // Crashes here
CoreDispatcher dispatcher = window.Dispatcher();
dispatcher.ProcessEvents(CoreProcessEventsOption::ProcessUntilQuit);
}
void SetWindow(CoreWindow const &) {
Compositor compositor;
ContainerVisual root = compositor.CreateContainerVisual();
m_target = compositor.CreateTargetForCurrentView();
m_target.Root(root);
}
};
int __stdcall wWinMain(HINSTANCE, HINSTANCE, PWSTR, int) { CoreApplication::Run(make<App>()); }
I've tried using window.Dispatcher().HasThreadAccess() to verify that I'm on the correct thread to be making UI calls, and it always returns true.
I've also tried calling RunAsync() from the window's Dispatcher and constructing a Xaml object in a lambda passed to this method, and it still has exactly the same result. HasThreadAccess returns true here too.
Can anyone explain to me where I'm going wrong here? Is constructing Xaml objects not supported in C++?
[edit]
Here's a sample project that reproduces the issue, again based on the default CoreWindow C++/WinRT template:
https://github.com/lyptt/CoreApp1
Turns out the CoreApplication-based template does not support anything from the Xaml namespace, as it's intended more towards providing a thin UWP layer for games, etc.
To get Xaml support you need to use the full template instead, then things magically start to work.
I am trying to convert an open source flyout menu from Objective-C to Xamarin. The current issue I have is that the Obj-C code creates a frame using CGRectInfinite. This does not appear to be available under MonoTouch, via the usual RectangleF class. Is there an alternative?
Similarly, there does not appear to be a CGRectIsInfinite equivalent in RectangleF. What, if any, is the alternative?
Add this using statement first:
using MonoTouch.CoreGraphics;
Then you can test it with this:
public static RectangleF GetInfinite()
{
var image = CIImage.EmptyImage;
if (image.Extent.IsInfinite ())
{
return image.Extent;
}
throw new Exception ("Unable to create infinite rect");
}
I have a vendor supplied .DLL and an online API that I am using to interact with a piece of radio hardware; I am using JNA to access the exported functions through Java (because I don't know C/C++). I can call basic methods and use some API structures successfully, but I am having trouble with the callback structure. I've followed the TutorTutor guide here and also tried Mr. Wall's authoritative guide here, but I haven't been able to formulate the Java side syntax for callbacks set in a structure correctly.
I need to use this exported function:
BOOL __stdcall SetCallbacks(INT32 hDevice,
CONST G39DDC_CALLBACKS *Callbacks, DWORD_PTR UserData);
This function references the C/C++ Structure:
typedef struct{
G39DDC_IF_CALLBACK IFCallback;
//more omitted
} G39DDC_CALLBACKS;
...which according to the API has these Members (Note this is not an exported function):
VOID __stdcall IFCallback(CONST SHORT *Buffer, UINT32 NumberOfSamples,
UINT32 CenterFrequency, WORD Amplitude,
UINT32 ADCSampleRate, DWORD_PTR UserData);
//more omitted
I have a G39DDCAPI.java where I have loaded the DLL library and reproduced the API exported functions in Java, with the help of JNA. Simple calls to that work well.
I also have a G39DDC_CALLBACKS.java where I have implemented the above C/C++ structure in a format works for other API structures. This callback structure is where I am unsure of the syntax:
import java.util.Arrays;
import java.util.List;
import java.nio.ShortBuffer;
import com.sun.jna.Structure;
import com.sun.jna.platform.win32.BaseTSD.DWORD_PTR;
import com.sun.jna.win32.StdCallLibrary.StdCallCallback;
public class G39DDC_CALLBACKS extends Structure {
public G39DDC_IF_CALLBACK IFCallback;
//more omitted
protected List getFieldOrder() {
return Arrays.asList(new String[] {
"IFCallback","DDC1StreamCallback" //more omitted
});
}
public static interface G39DDC_IF_CALLBACK extends StdCallCallback{
public void invoke(ShortBuffer _Buffer,int NumberOfSamples,
int CenterFrequency, short Amplitude,
int ADCSampleRate, DWORD_PTR UserData);
}
}
Edit: I made my arguments more type safe as Technomage suggested. I am still getting a null pointer exception with several attempts to call the callback. Since I'm not sure of my syntax regarding the callback structure above, I can't pinpoint my problem in the main below. Right now the relevant section looks like this:
int NumberOfSamples=65536;//This is usually 65536.
ShortBuffer _Buffer = ShortBuffer.allocate(NumberOfSamples);
int CenterFrequency=10000000;//Specifies center frequency (in Hz) of the useful band
//in received 50 MHz wide snapshot.
short Amplitude=0;//The possible value is 0 to 32767.
int ADCSampleRate=100;//Specifies sample rate of the ADC in Hz.
DWORD_PTR UserData = null;
G39DDC_CALLBACKS callbackStruct= new G39DDC_CALLBACKS();
lib.SetCallbacks(hDevice,callbackStruct,UserData);
//hDevice is a handle for the hardware device used-- works in other uses
//lib is a reference to the library in G39DDCAPI.java-- works in other uses
//The UserData is a big unknown-- I don't know what to do with this variable
//as a DWORD_PTR
callbackStruct.IFCallback.invoke(_Buffer, NumberOfSamples, CenterFrequency,
Amplitude, ADCSampleRate, UserData);
EDIT NO 2:
I have one callback working somewhat, but I don't have control over the buffers. More frustratingly, a single call to invoke the method will result in several runs of the custom callback, usually with multiple output files (results vary drastically from run to run). I don't know if it is because I am not allocating memory correctly on the Java side, because I cannot free the memory on the C/C++ side, or because I have no cue on which to tell Java to access the buffer, etc. Relevant code looks like:
//before this, main method sets library, starts DDCs, initializes some variables...
//API call to start IF
System.out.print("Starting IF... "+lib.StartIF(hDevice, Period)+"\n")
G39DDC_CALLBACKS callbackStructure = new G39DDC_CALLBACKS();
callbackStructure.IFCallback = new G39DDC_IF_CALLBACK(){
#Override
public void invoke(Pointer _Buffer, int NumberOfSamples, int CenterFrequency,
short Amplitude, int ADCSampleRate, DWORD_PTR UserData ) {
//notification
System.out.println("Invoked IFCallback!!");
try {
//ready file and writers
File filePath = new File("/users/user/G39DDC_Scans/");
if (!filePath.exists()){
System.out.println("Making new directory...");
filePath.mkdir();
}
String filename="Scan_"+System.currentTimeMillis();
File fille= new File("/users/user/G39DDC_Scans/"+filename+".txt");
if (!fille.exists()) {
System.out.println("Making new file...");
fille.createNewFile();
}
FileWriter fw = new FileWriter(fille.getAbsoluteFile());
//callback body
short[] deBuff=new short[NumberOfSamples];
int offset=0;
int arraySize=NumberOfSamples;
deBuff=_Buffer.getShortArray(offset,arraySize);
for (int i=0; i<NumberOfSamples; i++){
String str=deBuff[i]+",";
fw.write(str);
}
fw.close();
} catch (IOException e1) {
System.out.println("IOException: "+e1);
}
}
};
lib.SetCallbacks(hDevice, callbackStructure,UserData);
System.out.println("Main, before callback invocation");
callbackStructure.IFCallback.invoke(s_Pointer, NumberOfSamples, CenterFrequency, Amplitude, ADCSampleRate, UserData);
System.out.println("Main, after callback invocation");
//suddenly having trouble stopping DDCs or powering off device; assume it has to do with dll using the functions above
//System.out.println("StopIF: " + lib.StopIF(hDevice));//API function returns boolean value
//System.out.println("StopDDC2: " + lib.StopDDC2( hDevice, Channel));
//System.out.println("StopDDC1: " + lib.StopDDC1( hDevice, Channel ));
//System.out.println("test_finishDevice: " + test_finishDevice( hDevice, lib));
System.out.println("Program Exit");
//END MAIN METHOD
You need to extend StdCallCallback, for one, otherwise you'll likely crash when the native code tries to call the Java code.
Any place you see a Windows type with _PTR, you should use a PointerType - the platform package with JNA includes definitions for DWORD_PTR and friends.
Finally, you can't have a primitive array argument in your G39DDC_IF_CALLBACK. You'll need to use Pointer or an NIO buffer; Pointer.getShortArray() may then be used to extract the short[] by providing the desired length of the array.
EDIT
Yes, you need to initialize your callback field in the callbacks structure before passing it into your native function, otherwise you're just passing a NULL pointer, which will cause complaints on the Java or native side or both.
This is what it takes to create a callback, using an anonymous instance of the declared callback function interface:
myStruct.callbackField = new MyCallback() {
public void invoke(int arg) {
// do your stuff here
}
};
The documentation for ResizeSettings says:
"Replaced by the Instructions class"
http://documentation.imageresizing.net/docu/ImageResizer/ResizeSettings.htm
The documentation for Instructions says:
"The successor to ResizeSettings."
http://documentation.imageresizing.net/docu/ImageResizer/Instructions.htm
However, I cannot figure out how to use Instructions instead of ResizeSettings. I've tried
Google
Documentation (documentation.imageresizing.net)
Looking through the Object Browser for uses of Instructions
Searching ImageResizer.dll in .net Reflector for uses of Instructions
Decompiling all of ImageResizer.dll and searching for through the resulting code.
If Instructions replaces ResizeSettings, then how do I use it instead of ResizeSettings?
=== Edit - more detail:
This a way to use ResizeSettings:
public static Bitmap Resize(Bitmap bitmap, int maxHeight, int maxWidth)
{
var setting = new ResizeSettings
{
MaxHeight = maxHeight,
MaxWidth = maxWidth,
};
return ImageBuilder.Current.Build(bitmap, setting);
}
Reading that Instructions was a replacement for ResizeSettings, one of the first things I tried was this: (I was hoping ImageBuilder might have an overloaded Build method)
public static Bitmap Resize(Bitmap bitmap, int maxHeight, int maxWidth)
{
var instructions = new Instructions
{
Width = maxWidth,
Height = maxHeight,
Mode = FitMode.Max
};
return ImageBuilder.Current.Build(bitmap, instructions);
}
In an unexpected turn of events, the documentation is ahead of reality.
You can use the Instructions class, but for now you must convert it to a ResizeSettings instance first like so:
.Build(source, dest, new ResizeSettings(new Instructions("width=20")));
In the next major release, this will accept an Instructions class directly.