mouse_wheel

event<control, mouse_event_handler> xtd::forms::control::mouse_wheel

Occurs when the mouse wheel moves while the xtd::forms::control has focus.

Remarks

When handling the xtd::forms::control::mouse_wheel event it is important to follow the user interface (UI) standards associated with the mouse wheel. The mouse_event_args::delta property value indicates the amount the mouse wheel has been moved. The UI should scroll when the accumulated delta is plus or minus 120. The UI should scroll the number of logical lines returned by the system_information::mouse_wheel_scroll_lines property for every delta value reached. You can also scroll more smoothly in smaller that 120 unit increments, however the ratio should remain constant, that is system_information::mouse_wheel_scroll_lines lines scrolled per 120 delta units of wheel movement.

Mouse events occur in the following order:

1. xtd::forms::control::mouse_enter
2. xtd::forms::control::mouse_move
3. xtd::forms::control::mouse_hover / xtd::forms::control::mouse_down / xtd::forms::control::mouse_wheel / xtd::forms::control::mouse_horizontal_wheel
4. xtd::forms::control::mouse_up
5. xtd::forms::control::mouse_leave

Note

The following events are not raised for the tab_control class unless there is at least one tab_page in the tab_control::tab_pages collection: xtd::forms::control::click, xtd::forms::control::double_click, xtd::forms::control::mouse_down, xtd::forms::control::mouse_up, xtd::forms::control::mouse_hover, xtd::forms::control::mouse_enter, xtd::forms::control::mouse_leave and xtd::forms::control::mouse_move. If there is at least one tab_page in the collection, and the user interacts with the tab control's header (where the tab_page names appear), the tab_control raises the appropriate event. However, if the user interaction is within the client area of the tab page, the tab_page raises the appropriate event.

Examples

The following code example demonstrates the use of control mouse events.

#define TRACE
#include <xtd/forms/application>
#include <xtd/forms/form>
#include <xtd/forms/trace_form>
#include <xtd/diagnostics/trace>
 
using namespace xtd;
using namespace xtd::forms;
 
class form1 : public form {
public:
  form1() {
    text("Mouse events example");
    
    click += [&] {
      xtd::diagnostics::trace::write_line("click");
    };
    
    double_click += [&] {
      xtd::diagnostics::trace::write_line("double_click");
    };
    
    mouse_click += [&](object & sender, const mouse_event_args & e) {
      xtd::diagnostics::trace::write_line("mouse_click={{button={}, clicks={}, delta={}, location=[{}], modifier_keys=[{}]}}", e.button(), e.clicks(), e.delta(), e.location(), modifier_keys());
    };
    
    mouse_double_click += [&](object & sender, const mouse_event_args & e) {
      xtd::diagnostics::trace::write_line("mouse_double_click={{button={}, clicks={}, delta={}, location=[{}], modifier_keys=[{}]}}", e.button(), e.clicks(), e.delta(), e.location(), modifier_keys());
    };
    
    mouse_down += [&](object & sender, const mouse_event_args & e) {
      xtd::diagnostics::trace::write_line("mouse_down={{button={}, clicks={}, delta={}, location=[{}], modifier_keys=[{}]}}", e.button(), e.clicks(), e.delta(), e.location(), modifier_keys());
    };
    
    mouse_enter += [&] {
      xtd::diagnostics::trace::write_line("mouse_enter");
    };
    
    mouse_horizontal_wheel += [&](object & sender, const mouse_event_args & e) {
      xtd::diagnostics::trace::write_line("mouse_horizontal_wheel={{button={}, clicks={}, delta={}, location=[{}], modifier_keys=[{}]}}", e.button(), e.clicks(), e.delta(), e.location(), modifier_keys());
    };
    
    mouse_leave += [&] {
      xtd::diagnostics::trace::write_line("mouse_leave");
    };
    
    mouse_move += [&](object & sender, const mouse_event_args & e) {
      xtd::diagnostics::trace::write_line("mouse_move={{button={}, clicks={}, delta={}, location=[{}], modifier_keys=[{}]}}", e.button(), e.clicks(), e.delta(), e.location(), modifier_keys());
    };
    
    mouse_up += [&](object & sender, const mouse_event_args & e) {
      xtd::diagnostics::trace::write_line("mouse_up={{button={}, clicks={}, delta={}, location=[{}], modifier_keys=[{}]}}", e.button(), e.clicks(), e.delta(), e.location(), modifier_keys());
    };
    
    mouse_wheel += [&](object & sender, const mouse_event_args & e) {
      xtd::diagnostics::trace::write_line("mouse_wheel={{button={}, clicks={}, delta={}, location=[{}], modifier_keys=[{}]}}", e.button(), e.clicks(), e.delta(), e.location(), modifier_keys());
    };
  }
};
 
auto main() -> int {
  trace_form trace_form;
  application::run(form1 {});
}

Remarks

For more information about handling events, see Handling and Raising Events.