I have finished my first Qt application, and noticed that the QApplication constructor in the main.cpp files take up to 10 seconds to execute. This results in an annoying startup delay where I can't even show a splash screen.
When profiling this delay it turns out that the initializeMultitouch_sys method in the QApplicationPrivate class is the culprit. Specifically, the iInkTablets->get_Count(...) call takes all the time.
void QApplicationPrivate::initializeMultitouch_sys()
{
[...]
IInkTablets *iInkTablets = 0;
HRESULT hr = CoCreateInstance(QT_CLSID_InkTablets, NULL, CLSCTX_ALL, QT_IID_IInkTablets, (void**)&iInkTablets);
if (SUCCEEDED(hr)) {
long count = 0;
iInkTablets->get_Count(&count); // <== Takes 5-10 seconds!!
for (long i = 0; i < count; ++i) {
[...]
}
}
I am using Windows 7, but not utilizing any multi-touch feature. Any idea what causes this problem and how I can avoid it?
Thanks,
Fabian
UPDATE 2010-11-14 - PROBLEM SOLVED
I noticed that the problem then occured with all Qt based applications, including Qt Designer. A reboot fixed it.
This is fixed in 4.6.3 (QTBUG-6007/commit)
Related
Qt: 5.14.1
SDL: 2.0.12
OS: Windows 10
I'm working on a video player and I'm using Qt for UI and SDL for rendering frames.
I created the SDL window by passing my rendering widget's (inside a layout) winId() handle.
This works perfectly when I start a non-threaded Play().
However, this causes some issues with playback when resizing or moving the app window. Nothing serious, but since the play code is non threaded my frame queues fill-up which then causes the video to speed up until it catches to the audio.
I solved that by putting my play code inside Win32 thread created with CreateThread function.
Now when I move window the video continues to play as intended, but when resizing the app, rendering widget will stop refreshing the widget and only the last displayed frame before resize event will be shown.
I can confirm that video is still running and correct frames are still being displayed. The displayed image can even be resized, but its never refreshed.
The similar thing happens when I was testing Qt threads with SDL. Consider this code
class TestThread: public QThread
{
public:
TestThread(QObject *parent = NULL) : QThread(parent)
{
}
void run() override
{
for (;;)
{
SDL_Delay(1000/60);
// Basic square bouncing animation
SDL_Rect spos;
spos.h = 100;
spos.w = 100;
spos.y = 100;
spos.x = position;
SDL_SetRenderDrawColor(RendererRef, 0, 0, 0, 255);
SDL_RenderFillRect(RendererRef, 0);
SDL_SetRenderDrawColor(RendererRef, 0xFF, 0x0, 0x0, 0xFF);
SDL_RenderFillRect(RendererRef, &spos);
SDL_RenderPresent(RendererRef);
if (position >= 500)
dir = 0;
else if (position <= 0)
dir = 1;
if (dir)
position += 5;
else
position -= 5;
}
}
};
// a call from Init SDL and Start Thread button
...
// create new SDL borderless resizible window.
WindowRef = SDL_CreateWindow("test",10,10,1280,800,SDL_WINDOW_RESIZABLE | SDL_WINDOW_BORDERLESS);
// create and start thread
test_thread = new TestThread();
test_thread->start();
...
This will create a separate window from the Qt app window and will start rendering a bouncy square. However if any resize event occurs in the Qt app, the rendering context will be lost and the the same thing that happens in my video player will happen here.
I also found out that If I remove SDL_RenderPresent function from the Thread object and put it in a Main Qt Window, the rendering will continue after resize event. However this has proved as completely unreliable and will sometimes completely freeze my app.
I also can't figure out why my completely separate SDL window and renderer still freezes on resize.
I presume there is a clash somewhere with SDL renderer/window and Qt's drawing stuff, but I'm at a loss here.
Also, it's only the resize stuff. Everything else works.
Thanks.
Answer:
SDL_Renderer needs to be destroyed and recreated on window resize as well as any SDL_Texture created with previous renderer.
The same thing will happen even without qt.
However, I think this is just a workaround and not a real solution.
A simple code to recreate the issue.
int position = 0;
int dir = 0;
SDL_Window *window = NULL;
SDL_Renderer *sdlRenderer_ = NULL;
DWORD WINAPI MyThreadFunction( LPVOID lpParam )
{
for (;;)
{
SDL_Delay(1000/60);
// Basic square bouncing animation
SDL_Rect spos;
spos.h = 100;
spos.w = 100;
spos.y = 100;
spos.x = position;
SDL_SetRenderDrawColor(sdlRenderer_, 0, 0, 0, 255);
SDL_RenderFillRect(sdlRenderer_, 0);
SDL_SetRenderDrawColor(sdlRenderer_, 0xFF, 0x0, 0x0, 0xFF);
SDL_RenderFillRect(sdlRenderer_, &spos);
SDL_RenderPresent(sdlRenderer_);
if (position >= 500)
dir = 0;
else if (position <= 0)
dir = 1;
if (dir)
position += 5;
else
position -= 5;
}
}
int APIENTRY wWinMain(_In_ HINSTANCE hInstance, _In_opt_ HINSTANCE hPrevInstance, _In_ LPWSTR lpCmdLine,_In_ int nCmdShow)
{
SDL_Init(SDL_INIT_VIDEO);
window = SDL_CreateWindow("test",SDL_WINDOWPOS_UNDEFINED,SDL_WINDOWPOS_UNDEFINED,600,600,SDL_WINDOW_SHOWN | SDL_WINDOW_RESIZABLE);
if (!window)
printf("Unable to create window");
sdlRenderer_ = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED |SDL_RENDERER_PRESENTVSYNC | SDL_RENDERER_TARGETTEXTURE);
if (!sdlRenderer_)
printf("Unable to create renderer");
HANDLE playHandle = CreateThread(0, 0, MyThreadFunction, 0, 0, 0);
if (playHandle == NULL)
{
return 0;
}
SDL_Event e;
while(1)
{
SDL_PollEvent(&e);
if (e.type == SDL_WINDOWEVENT )
{
switch( e.window.event )
{
case SDL_WINDOWEVENT_SIZE_CHANGED:
int mWidth = e.window.data1;
int mHeight = e.window.data2;
SDL_DestroyRenderer(sdlRenderer_); // stops rendering on resize if commented out
sdlRenderer_ = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED |SDL_RENDERER_PRESENTVSYNC | SDL_RENDERER_TARGETTEXTURE);
break;
}
}
}
return 0;
}
EDIT:
Real solution.
Renderer doesn't need to be recreated. Seperate the Qt code from SDL main thread by making a seperate thread. Create all SDL stuff in that thread because SDL_Renderer needs to be created in a thread that handles SDL events.
Use SDL_PushEvent to signal this thread to render to screen.
This way textures don't need to be recreated.
I'm building a Othello game in Qt quick and C++.
I use this code from QML dialog to start new game, when one player is human, I wait for input. When two players are PC, I face the problem that the GUI will wait for the slot to finish, in PC players the slot call flipTurn() (because it is PC, no input to wait for), flipTurn is recursive, so the GUI will block until the game end.
I want it to update the board after each move. link for the project:
reversi project
myBroker.createGame(blacktypebutton.checkedButton.playertype,
whitetypebutton.checkedButton.playertype,
getBlackAlgo(),
getWhiteAlgo(),
getBlackDep(),
getWhiteDep());
console.log("finished creating game !");
void Broker::flipTurn()
{
if(someoneWon()){
emit gameEnd();
return;
}
emit updateBoard();
if (currentGame->getTurn() == Constants::BLACK){
currentGame->setTurn(Constants::WHITE);
if (currentGame->getWhitePlayer().getType() == Constants::PC){
currentGame->pcMove(Constants::WHITE);
flipTurn();
}
else
currentGame->updatePossible();
}
else{
currentGame->setTurn(Constants::BLACK);
if (currentGame->getBlackPlayer().getType() == Constants::PC){
currentGame->pcMove(Constants::BLACK);
flipTurn();
}
else
currentGame->updatePossible();
return;
}
emit updateBoard();
}
bool Broker::createGame(int blacktype, int whitetype, int blackalg, int whitealg, int blackdep, int whitedep)
{
currentGame = new Game(blacktype,whitetype,blackalg,whitealg,blackdep,whitedep);
currentGame->setGameBoard(&gameBoard);
updatePossible();
emit gameStart();
}
void Broker::onGameStart()
{
if(currentGame->getTurnType() == Constants::PC){
currentGame->pcMove(currentGame->getTurn());
cout<<"in ongamestart slot"<<endl;
flipTurn();
}
}
Since it is a turn based game, you will just need a different source to trigger the next turn.
Instead of calling flipTurn() directly, you call it through Qt's event loop.
Since you probably will want the human in front of the computer to see the game progressing, very likely with a delay.
For example with a single shot timer
// instead of calling flipTurn() directly
QTimer::singleShot(500, this, SLOT(flipTurn()));
Call next flipTurn() after 500 milliseconds.
I used
QCoreApplication::processEvents();
After each call to flipTurn() , so the GUI engine process any waiting signals (in my case the updateBoard() signal).
Although it isn't the best solution, it worked well for my homework.
I have an Qt based OpenGLES2.0 application, where I want to capture the FPS.
my application draw same geometry for 16 times and then try to know the FPS.
How can I make sure glDrawElements() has finished its job ?
I want to get the correct FPS.
Is there any way to make the glDrawElements()synchronous or Pooling the glDrawElements() complete?
define a Timer object in application window/widget class.
QTime frameTime;
Start the timer in initializeGL.
frameTime.start();
in PaintGL
paintGL ()
{
draw_your_geometry();
++frameCount;
if (frameTime.elapsed() >= 1000)
{
double fps = frameCount / ((double)frameTime.elapsed()/1000.0);
}
}
I have a solution which includes three projects. one is creating static library i.e .lib file. It contains one header file main.h and one main.cpp file. cpp file contains the definition of functions of header file.
second project is .exe project which includes the header file main.h and calls a function of header file.
third project is also a .exe project which includes the header file and uses a variable flag of header file.
Now both .exe projects are creating different instance of the variable. But I want to share same instance of the variable between the projects dynamically. as I have to map the value generated by one project into other project at the same instant.
Please help me as I am nearing my project deadline.
Thanks for the help.
Here are some part of the code.
main.cpp and main.h are files of .lib project
main.h
extern int flag;
extern int detect1(void);
main.cpp
#include<stdio.h>
#include"main.h"
#include <Windows.h>
#include <ShellAPI.h>
using namespace std;
using namespace cv;
int flag=0;
int detect1(void)
{
int Cx=0,Cy=0,Kx=20,Ky=20,Sx=0,Sy=0,j=0;
//create the cascade classifier object used for the face detection
CascadeClassifier face_cascade;
//use the haarcascade_frontalface_alt.xml library
face_cascade.load("E:\\haarcascade_frontalface_alt.xml");
//System::DateTime now = System::DateTime::Now;
//cout << now.Hour;
//WinExec("E:\\FallingBlock\\FallingBlock\\FallingBlock\\bin\\x86\\Debug\\FallingBlock.exe",SW_SHOW);
//setup video capture device and link it to the first capture device
VideoCapture captureDevice;
captureDevice.open(0);
//setup image files used in the capture process
Mat captureFrame;
Mat grayscaleFrame;
//create a window to present the results
namedWindow("capture", 1);
//create a loop to capture and find faces
while(true)
{
//capture a new image frame
captureDevice>>captureFrame;
//convert captured image to gray scale and equalize
cvtColor(captureFrame, grayscaleFrame, CV_BGR2GRAY);
equalizeHist(grayscaleFrame, grayscaleFrame);
//create a vector array to store the face found
std::vector<Rect> faces;
//find faces and store them in the vector array
face_cascade.detectMultiScale(grayscaleFrame, faces, 1.1, 3, CV_HAAR_FIND_BIGGEST_OBJECT|CV_HAAR_SCALE_IMAGE, Size(30,30));
//draw a rectangle for all found faces in the vector array on the original image
for(unsigned int i = 0; i < faces.size(); i++)
{
Point pt1(faces[i].x + faces[i].width, faces[i].y + faces[i].height);
Point pt2(faces[i].x, faces[i].y);
rectangle(captureFrame, pt1, pt2, cvScalar(0, 255, 0, 0), 1, 8, 0);
if(faces.size()>=1)
j++;
Cx = faces[i].x + (faces[i].width / 2);
Cy = faces[i].y + (faces[i].height / 2);
if(j==1)
{
Sx=Cx;
Sy=Cy;
flag=0;
}
}
if(Cx-Sx > Kx)
{
flag = 1;
printf("%d",flag);
}
else
{
if(Cx-Sx < -Kx)
{
flag = 2;
printf("%d",flag);
//update(2);
}
else
{
if(Cy-Sy > Ky)
{
flag = 3;
printf("%d",flag);
//update(3);
}
else
{
if(Cy-Sy < -Ky)
{
flag = 4;
printf("%d",flag);
//update(4);
}
else
if(abs(Cx-Sx) < Kx && abs(Cy-Sy)<Ky)
{
flag = 0;
printf("%d",flag);
//update(0);
}
}
}
}
2nd project's code
face.cpp
#include"main.h"
#include<stdio.h>
int main()
{
detect1();
}
3rd project's code
tetris.cpp
#include"main.h"
int key;
key = flag;
if(key==0)
{
MessageBox(hwnd,"Space2","TetRiX",0);
}
if(key==4)
{
tetris.handleInput(1);
tetris.drawScreen(2);
//MessageBox(hwnd,"Space2","TetRiX",0);
}
You need to look up how to do inter-process communication in the operating system under which your applications will run. (At this point I assume that the processes are running on the same computer.) It looks like you're using Windows (based on seeing a call to "MessageBox") so the simplest means would be for both processes to use RegisterWindowMessage create a commonly-understood message value, and then send the data via LPARAM using either PostMessage or SendMessage. (You'll need each of them to get the window handle of the other, which is reasonably easy.) You'll want to have some sort of exclusion mechanism (mutex or critical section) in both processes to ensure that the shared value can't be read and written at the same time. If both processes can do the "change and exchange" then you'll have an interesting problem to solve if both try to do that at the same time, because you'll have to deal with the possibility of deadlocks over that shared value.
You can also use shared memory, but that's a bit more involved.
If the processes are on different computers you'll need to do it via TCP/IP or a protocol on top of TCP/IP. You could use a pub-sub arrangement--or any number of things. Without an understanding of exactly what you're trying to accomplish, it's difficult to know what to recommend.
(For the record, there is almost no way in a multi-process/multi-threaded O/S to share something "at the same instant." You can get arbitrarily close, but computers don't work like that.)
Given the level of difficulty involved, is there some other design that might make this cleaner? Why do these processes have to exchange information this way? Must it be done using separate processes?
In QT have the following code that starts a thread to send out commands. The thread takes a char * and int as arguments. In the "run" I use the pointer that is given by the constuctor. The code is:
MyThread::MyThread(char * payld, int payld_size)
{
payload_size = payld_size;
payload_p = payld;
}
void MyThread::run()
{
while(...)
{
sendCommand(payload_p, payload_size);
}
}
Unfortunately this doesn´t work and my application crashes when I try to use thread.start(). But when I change it to:
MyThread::MyThread(char * payld, int payld_size)
{
payload_size = payld_size;
payload_p = payld;
for(int i=0; i<payload_size; i++)
{
payload[i] = payld[i];
}
}
void MyThread::run()
{
while(...)
{
sendCommand(payload, payload_size);
}
}
The code does run and only crashes sometimes (looks pretty random to me). Can anybody Explain me why version one doesnt work and version two does? And any ideas on why the second code sometimes crashes? Could it be because the size of payload is not predefined (in the header file I defined it as
char payload[];
When I define it as:
char payload[10];
it seems to work better, but it is annoying to test since the crashes are pretty random.
instead of fiddling with char*, I would switch to QString (since you're using Qt). It takes a bit of learning, but it's almost mandatory to get code working smoothly in this framework. Then declare
QString payload;
and depending on sendCommand implementation, use one of the member functions QString to get the char*, like payload.toLatin1()