Mouse

cvui has its own mouse API to track mouse clicks and cursor position, for instance. Everything related to the mouse can be accessed from cvui::mouse(). The following sections will detail all mouse information available.

Cursor position

You can query the position of the mouse cursor any moment by calling cvui::mouse(), which returns a cv::Point:

cv::Point mouse(const cv::String& theWindowName = "")

Usage example:

// Save the mouse cursor to a point object
cv::Point cursor = cvui::mouse();
std::cout << "x: " << cursor.x << " y: " << cursor.y << std::endl;

// or access the position directly
std::cout << "x: " << cvui::mouse().x << " y: " << cvui::mouse().y << std::endl;

Calls to cvui::mouse() follow the cvui philosophy of always returning current information, so you don’t have to listen to mouse events, for instance. Just call cvui::mouse() and you get the most up-to-date position of the mouse cursor.

Detect events, e.g. clicks

You can query the state of the mouse, e.g. clicks, by calling cvui::mouse(int), whose signature is:

bool mouse(int theQuery)

The parameter theQuery is an integer that specifies your query. Available queries are:

• cvui::DOWN: query if any mouse button was pressed. cvui::mouse() returns true for a single frame only (the one a mouse button went down).
• cvui::UP: query if any mouse button was released. cvui::mouse() returns true for a single frame only (the one a mouse button went up).
• cvui::CLICK: query if any mouse button was clicked (went down then up, no matter the amount of frames in between). cvui::mouse() returns true for a single frame only.
• cvui::IS_DOWN: query if any mouse button is currently pressed. cvui::mouse() returns true for as long as the button is down/pressed.

Below is an example that shows a message when any mouse button is pressed:

if (cvui::mouse(cvui::DOWN)) {
	std::cout << "Any mouse button just went down." << std::endl;
}

Below is an example that shows a message only when any mouse button is clicked (pressed then released):

if (cvui::mouse(cvui::CLICK)) {
	std::cout << "A mouse click just happened." << std::endl;
}

Check mouse buttons individually

You can also query the state of a particular mouse button, e.g. react to clicks on the left button of the mouse.

Specific mouse buttons can be queried via cvui::mouse(int, int), whose signature is:

bool mouse(int theButton, int theQuery)

The parameter theButton allows you to specify which mouse button you want to query. Available buttons are cvui::LEFT_BUTTON, cvui::MIDDLE_BUTTON and cvui::RIGHT_BUTTON.

The function cvui::mouse(int theButton, int theQuery) works exactly as cvui::mouse(int theQuery) does, the only difference is that queries are target at a particular button, not all buttons.

Below is an example that prints a message when the left mouse button is pressed:

if (cvui::mouse(cvui::LEFT_BUTTON, cvui::DOWN)) {
	std::cout << "Left mouse button just went down." << std::endl;
}

Here is another example that shows a message only when the left mouse button is clicked (pressed then released):

if (cvui::mouse(cvui::LEFT_BUTTON, cvui::CLICK)) {
	std::cout << "Left mouse button click just happened." << std::endl;
}

Learn more

Check out the mouse, mouse-complex and mouse-complex-buttons examples for more information about cvui’s mouse API.