MyCanvas_2D class

This is a sub-class of the Canvas_2D class, to deal especifically with axes that present only 2D behavior, on the CanvasMouseEvents educational app.

Contents

Authors

History

@version 1.00

Initial version: August 2021

Adapted from the code initially prepared for the course CIV 2801 - Fundamentos de Computação Gráfica, 2021, second term, Department of Civil Engineering, PUC-Rio.

Class definition

classdef MyCanvas_2D < Canvas_2D

Private properties - mouse events

    properties (SetAccess = private, GetAccess = private)
        firstPosition = [];         % x and y coordinates of the first pointer position.
        firstPositionGiven = false; % flag indicating that first point was selected.
        lineDisplayed = false;      % flag indicating that a line was displayed.
        clr = [0 0 1];              % color to be used for plots (blue)
        markSize = 0.01;            % radius of circle mark.
        xLim_mSz = 150;             % Proportionality constant (xLim/markSize)

        % handles to plots (for quick access)
        h_mark_1 = [];
        h_mark_2 = [];
        h_line   = [];

        draw = []; % handle to object that draws on canvas
    end

Constructor method

    methods
        function this = MyCanvas_2D(ax,fig,fcn)
            if (nargin == 0)
                ax  = [];
                fig = [];
                fcn = [];
            elseif (nargin <= 2)
                fcn = [];
            end
            this = this@Canvas_2D(ax,fig,fcn);

            % Creates an object to draw on canvas:
            % <drawoncanvas.html *DrawOnCanvas*> class.
            this.draw = DrawOnCanvas(this);
        end
    end

Public methods

Implementation of the methods that act as mouse event callbacks.

    methods
        %------------------------------------------------------------------
        % Mouse button down callback - generic callback, called from an
        % Emouse object.
        % Input:
        % * this  = handle to this canvas object
        % * pt    = current cursor coordinates
        % * whichMouseButton = 'left', 'right', 'center', 'double click'
        function onButtonDown(this,pt,whichMouseButton)
            % Compute mark size, based on canvas x limits
            this.markSize = diff(this.ax.XLim) / this.xLim_mSz;

            %%%%%%% COMPLETE HERE - MOUSEVENTS: 01 %%%%%%%
            %%%%%%% COMPLETE HERE - MOUSEVENTS: 01 %%%%%%%
        end

        %------------------------------------------------------------------
        % Mouse button up callback - generic callback, called from an
        % Emouse object.
        % Input:
        % * this  = handle to this canvas object
        % * pt    = current cursor coordinates
        % * whichMouseButton = 'left', 'right', 'center', 'double click'
        function onButtonUp(this,~,~)
        %%%%%%% COMPLETE HERE - MOUSEVENTS: 03 %%%%%%%
        %%%%%%% COMPLETE HERE - MOUSEVENTS: 03 %%%%%%%
        end

        %------------------------------------------------------------------
        % Mouse move callback - generic callback, called from an
        % Emouse object.
        % Input:
        % * this  = handle to this canvas object
        % * pt    = current cursor coordinates
        function onMouseMove(this,pt)
        %%%%%%% COMPLETE HERE - MOUSEVENTS: 02 %%%%%%%
        %%%%%%% COMPLETE HERE - MOUSEVENTS: 02 %%%%%%%
        end
    end

end

Published with MATLAB® R2026a