I'm creating a "dotted paper" component for my QML app. Essentially this components consists of a dotted background that the user can zoom upon. To create this I used the following code:
DottedPaper.qml
import QtQuick 2.15
Rectangle{
id: page
property int spacing: 50
// this property changes the spacing between the dots
property real contentScale: 1.0
Repeater{
id: rowRepeater
model: 200
Repeater{
id: row
property int rowIndex: index
model: 200
Rectangle{
id: circle
color: "red"
width: 4; height: 4
x: index * spacing * page.contentScale + width/2;
y: rowIndex * spacing * page.contentScale+ height/2
radius: width/2
}
}
}
}
Then in my main file I have the following:
import QtQuick 2.15
import QtQuick.Window 2.15
import QtQuick.Controls 2.15
Window {
width: 640
height: 480
visible: true
title: qsTr("Hello World")
Flickable{
clip: true // doesn't improve anything
anchors.fill: parent
contentWidth: paper.width
contentHeight: paper.height
DottedPaper{
id: paper
width: 10000; height: 10000;
clip: true
}
}
// the slider changes the content scale of the dotted paper
Slider{
from: 1
to: 3
onValueChanged: paper.contentScale = value
}
}
The problem with this code is that it's slow. Upon checking the application does not render the content at 60fps, but I get around 45 - 50 fps on my desktop. I suspect the issues is that QML is reevaluating the contentScale property binding for each circle in the background even if the circle is not visible on the screen. What is the best way to prevent this?
It works a lot better if you change your Repeaters to be ListViews. That's because a ListView is smart enough to only create enough delegates as needed for the visible space. (At first I thought a GridView would work, but that doesn't give you enough control over rows/columns.)
Rectangle{
id: page
property int cellWidth: 50 * contentScale
property int dotWidth: 4
// this property changes the spacing between the dots
property real contentScale: 1.0
ListView {
id: grid
model: 200
anchors.fill: parent
anchors.leftMargin: page.dotWidth / 2
anchors.topMargin: page.dotWidth / 2
spacing: page.cellWidth - page.dotWidth
delegate: ListView {
model: 200
width: window.width
height: page.dotWidth
orientation: ListView.Horizontal
spacing: page.cellWidth - page.dotWidth
property int rowIndex: index
delegate: Rectangle{
id: circle
color: "red"
width: page.dotWidth; height: page.dotWidth
radius: width/2
}
}
}
}
I'm using FabricJS in my web application. As I draw shapes, I notice that the control widget for all the objects are rectangular. Can the shape of a control widget be modified to fit the actual shape of the object? Say, a circle with a circular control widget.
I went through the Controls Customization demo. But there is no option to modify the shape of a control widget.
I need to modify the shape of the control widgets for the following purpose:
In my application whenever an object is clicked, its fill colour is toggled between black and white. In this case(refer the image below), because the circle has a rectangular control widget, clicking the pointed pixel selects the circle instead of the rectangle. I also hide the control widget from appearing by using hasControls property. So, the user will not know anything about the control widget. So, is the shape of the control widget editable?
I don't think there is an easy way to do that with fabric.js without writing a whole bunch of extra code. Fabric.js always draws a rectangle bounding box and uses it for selection controls. However, since you're planning on hiding the controls anyway, it sounds like you might be better off using perPixelTargetFind.
When true, object detection happens on per-pixel basis rather than on
per-bounding-box
Here's a quick demo:
const canvas = new fabric.Canvas('c', {
preserveObjectStacking: true,
perPixelTargetFind: true
})
const circle = new fabric.Circle({
radius: 50,
left: 50,
top: 50,
stroke:'green',
fill: 'white',
hasControls: false,
hasBorders: false
})
const rect = new fabric.Rect({
width: 200,
height: 150,
left: 50,
top: 25,
stroke: 'green',
fill: 'black',
hasControls: false,
hasBorders: false
})
canvas.on('mouse:down', (e) => {
const obj = e.target
if (obj) {
obj.set({
fill: obj.fill === 'white' ? 'black' : 'white'
})
canvas.requestRenderAll()
}
})
canvas.add(circle, rect)
circle.bringToFront()
canvas.requestRenderAll()
body {
background: ivory;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/3.4.0/fabric.min.js"></script>
<canvas id="c" width="300" height="200"></canvas>
I am working on a Gantt-like task display using HTML5 canvas, and the Konvajs canvas library.
Deconstructing a Gantt chart into its components leads me currently to a view as below. Here 1 is the list of tasks, 2 is the task bar area, 3 is a task bar, and 4 is a text cell.
For this question I am seeking code to construct 1 & 4. The data to be displayed will be delivered in plain JS objects with a nested list of tasks where each task has a number, name, assigned-to person name, start date, end date, days duration, and % complete.
So the requirement is to be able to construct a spreadsheet-like panel such as is seen on the left hand side of a Gantt chart.
I have something part developed which I shall post as an answer. However this seems like such as common need that I am hoping there is someone out there with code they can cut & paste into SO to lead the way.
Note: Gantt in sample image is from Vertex42.
So here is my own fumbling attempt at an approach. Can anyone improve upon it or am I going down the wrong road.
EDIT: I now have a fledgling component for drawing text into the spreadsheet-like cells, including the percent complete shading. To keep this answer uncluttered, this additional component is in this codepen.
// this is the object that defines our grid
//
var gridData = { name: 'grid1', width: 350, height: 400, rowHeight: 24, padding: 4, fill: 'azure', gridLineColor: '#ccc', header: {size: 16, fill: 'black', color: 'white' }, data: {size: 16, fill: 'azure', color: 'black' },
row: [
{ cells: // row 1
[
{ width: 50, text: 'Item', style: 'header'},
{ width: 240, text: 'Name', style: 'header'},
{ width: 60, text: 'Status', style: 'header'},
]
},
{ cells: // row 2
[
{ text: '1'},
{ text: 'Find tea pot'},
{ text: '100%'},
]
},
{ cells: // row 3
[
{ text: '2'},
{ text: 'Boil water'},
{ text: '60%'},
]
}
]
}
// From here on could be wrapped into a component that churns out grids. Maybe you pass in the id of the stage container
// and the data model you want to produce, etc.
// Set up the canvas / stage
var stage = new Konva.Stage({container: 'container1', width: 600, height: 300});
// Add a layer
var layer = new Konva.Layer({draggable: false});
stage.add(layer);
// make a main group for the grid, call it a panel. Assigning a name may be handy later
var panel = new Konva.Group({name: gridData.name});
layer.add(panel); // Add the panel to the layer
// a group has no visual properties. Add a background rect to hold the colour fill
var panelRect = new Konva.Rect({width: gridData.width, height: gridData.height, fill: gridData.fill})
panel.add(panelRect);
var topLeft = {x: 0, y: 0}; // Since we are drawing a grid, we need to compute the position of each cell
for (var i = 0; i < gridData.row.length; i = i + 1){
topLeft.x = 0; // reset x at start of each row
// iterate for each cell on the row
for (var j = 0; j < gridData.row[i].cells.length; j = j + 1){
var cell = new Konva.Rect({name: 'cellBg', // assign a name for later searching
x: topLeft.x, y: topLeft.y, // position as computed
width: gridData.row[0].cells[j].width, // use the first row from celldate to get the cell width
height: gridData.rowHeight, // grid has a uniform row height
stroke: gridData.gridLineColor, // and line colour
strokeWidth: 1, // use a set line width but you can add to the gridData object as needed.
fill: (i === 0 ? gridData.header.fill : gridData.data.fill), // use the given header text color
});
panel.add(cell);
// Add text to the cell. Note that if you wanted to be using alignments you would need to draw the text off-screen and
// get width/height of that text then use those values for positioning calculations. Once you have the rect size of the
// text, all the alignments are simple math.
var text = new Konva.Text({ x: topLeft.x + gridData.padding, // add padding to locate the text nicely into the cell
y: topLeft.y + gridData.padding,
// use the given text size
fontSize: (i === 0 ? gridData.header.size : gridData.data.size),
// use the given header text color
fill: (i === 0 ? gridData.header.color : gridData.data.color),
text: gridData.row[i].cells[j].text, // set the text value.
listening: false // stop text interfering with mouse events
});
panel.add(text);
cell.on('mouseover', function(evt){
var shape = evt.target;
$(shape).data('bgColor', shape.fill());
shape.fill('lime');
layer.draw();
})
cell.on('mouseout', function(evt){
var shape = evt.target;
shape.fill($(shape).data('bgColor'));
layer.draw();
})
topLeft.x = topLeft.x + gridData.row[0].cells[j].width; // offset the computed next cell x value by the width of the cell
}
topLeft.y = topLeft.y + gridData.rowHeight; // offset the computed next cell y value by the height of the row
}
layer.draw();
stage.draw();
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/konva/2.5.1/konva.min.js"></script>
<div id='container1' style="width: 300px, height: 200px; background-color: silver;"></div>
What I am attempting to do is anchor an Item over a particular place over an Image. The Image needs to use Image.PreserveAspectFit for the fillMode. The problem I am having is that the height/width/paintedWidth/paintedHeight of the Image are for the entire image "canvas" (I'm not sure what it's actually called), not the drawn part of the image itself. So I can't anchor to the actual image.
See code below for an example I tried with anchors (red rectangle) and with a child rectangle and x,y coordinates (green rectangle).
import QtQuick 2.3
import QtQuick.Window 2.2
Window {
visible: true
height: 400
width: 400
Image {
id: image
anchors.fill: parent
fillMode: Image.PreserveAspectFit
source: "image.jpg"
Rectangle {
id: bottomRight
width: 40
height: 40
color: "green"
x: parent.width * 0.75
y: parent.height * 0.75
}
}
Rectangle {
id: topLeft
width: 40
height: 40
color: "red"
anchors.top: image.top
anchors.left: image.left
anchors.topMargin: image.height * 0.25
anchors.leftMargin: image.width * 0.25
}
}
When you change the size of the window the placement of the rectangles is not in the same place over the image. I'd post some screenshots but I don't have enough reputation yet!
I poked around through the widget tree using the debugger but I can't seem to find any properties that provide the information about the scaling that I could use to calculate placement of the rectangles.
Update
I used the following functions to calculate the margins since I will be using potentially lots of these overlays.
function horMargin(val)
{
return ((image.width - image.paintedWidth)/2 + image.paintedWidth * val)
}
function verMargin(val)
{
return ((image.height - image.paintedHeight)/2 + image.paintedHeight * val)
}
Did you try to use paintedWidth and paintedHeight? :)
This will give you a rectangle that fills the painted image:
import QtQuick 2.3
import QtQuick.Window 2.2
Window {
visible: true
height: 400
width: 400
Image {
id: image
anchors.fill: parent
fillMode: Image.PreserveAspectFit
source: "image.jpg"
}
Rectangle {
x: (image.width - image.paintedWidth) / 2
y: (image.height - image.paintedHeight) / 2
width: image.paintedWidth
height: image.paintedHeight
color: "transparent"
border.color: "darkorange"
border.width: 2
}
}
From there, you can work out how to apply the margins that you need.
I am trying to implement an image viewer (sort of):
model/view approach
using both c++ and qml
the images are just a ListView filled up with Image (delegate) items
Here is a piece of code:
property double zoomFactor: 1.5;
property double imgScale: 1;
CustomToolBar
{
id: toolBar
onZoomInSignal:
{
imgScale = imgScale*zoomFactor;
}
onZoomOutSignal:
{
imgScale = imgScale/zoomFactor;
}
onZoomFitSignal:
{
imgScale = 1;
}
}
Rectangle
{
id: bgRect
Layout.fillWidth: true
Layout.fillHeight: true
color: "Grey"
anchors.margins: 10
ScrollView
{
id: scrollView
anchors.fill: parent
ListView
{
id: listView
anchors.fill: parent
clip: true
spacing: 10
model: listItemModel
anchors.top: parent.top
anchors.bottom: parent.bottom
anchors.left: parent.left
anchors.right: parent.right
anchors.margins: 10
boundsBehavior: Flickable.StopAtBounds
delegate: Image
{
id: item_id
anchors.horizontalCenter: parent.horizontalCenter
source: item_img_path + "/" + Math.random()
scale: imgScale
}
}
}
}
The images are loaded correctly, I need to be able to zoom them.
In order to zoom I just modify the scale property of the Image delegate.
Images not scaled (scale = 1) CORRECT:
Images unzoomed (scale = 1/1.5) WRONG! images spacing (?) is being incremented:
Images zoomed (scale = 1.5) WRONG! images overlap:
As you can see, zoom minus increments the spacing (I'm quite not sure it is really the spacing) between the images, and zoom plus overlaps the images.
Furthermore, it would be nice to have the horizontal scrollbar for the ScrollView when zooming in, but I cannot achieve this.
Can anyone help me?
Thanks
EDIT:
Following the solution proposed by grillvott the images are zoomed in/out correctly, but the whole ListView is getting smaller/bigger with them:
The result should be instead something like this (gimp mode ON):
Any idea?
I don't think that scale will take any boundaries into consideration. You could encapsulate the image and use fillMode to make sure the image scales accordingly:
delegate: Item {
anchors.horizontalCenter: parent.horizontalCenter
width: img.sourceSize.width * imgScale
height: img.sourceSize.height * imgScale
Image {
id: img
anchors.fill: parent
source: item_img_path + "/" + Math.random()
fillMode: Image.Stretch
}
}