I have 2 canvases, one uses HTML attributes width and height to size it, the other uses CSS:
<canvas id="compteur1" width="300" height="300" onmousedown="compteurClick(this.id);"></canvas>
<canvas id="compteur2" style="width: 300px; height: 300px;" onmousedown="compteurClick(this.id);"></canvas>
Compteur1 displays like it should, but not compteur2. The content is drawn using JavaScript on a 300x300 canvas.
Why is there a display difference?
It seems that the width and height attributes determine the width or height of the canvas’s coordinate system, whereas the CSS properties just determine the size of the box in which it will be shown.
This is explained in the HTML specification:
The canvas element has two attributes to control the size of the element’s bitmap: width and height. These attributes, when specified, must have values that are valid non-negative integers. The rules for parsing non-negative integers must be used to obtain their numeric values. If an attribute is missing, or if parsing its value returns an error, then the default value must be used instead. The width attribute defaults to 300, and the height attribute defaults to 150.
To set the width and height on a canvas, you may use:
canvasObject.setAttribute('width', '150');
canvasObject.setAttribute('height', '300');
For <canvas> elements, the CSS rules for width and height set the actual size of the canvas element that will be drawn to the page. On the other hand, the HTML attributes of width and height set the size of the coordinate system or 'grid' that the canvas API will use.
For example, consider this (jsfiddle):
var ctx = document.getElementById('canvas1').getContext('2d');
ctx.fillStyle = "red";
ctx.fillRect(10, 10, 30, 30);
var ctx2 = document.getElementById('canvas2').getContext('2d');
ctx2.fillStyle = "red";
ctx2.fillRect(10, 10, 30, 30);
canvas {
border: 1px solid black;
}
<canvas id="canvas1" style="width: 50px; height: 100px;" height="50" width="100"></canvas>
<canvas id="canvas2" style="width: 100px; height: 100px;" height="50" width="100"></canvas>
Both have had the same thing drawn on them relative to the internal coordinates of the canvas element. But in the second canvas, the red rectangle will be twice as wide because the canvas as a whole is being stretched across a bigger area by the CSS rules.
Note: If the CSS rules for width and/or height aren't specified then the browser will use the HTML attributes to size the element such that 1 unit of these values equals 1px on the page. If these attributes aren't specified then they will default to a width of 300 and a height of 150.
The canvas will be stretched if you set the width and height in your CSS. If you want to dynamically manipulate the dimension of the canvas you have to use JavaScript like so:
canvas = document.getElementById('canv');
canvas.setAttribute('width', '438');
canvas.setAttribute('height', '462');
The browser uses the css width and height, but the canvas element scales based on the canvas width and height. In javascript, read the css width and height and set the canvas width and height to that.
var myCanvas = $('#TheMainCanvas');
myCanvas[0].width = myCanvas.width();
myCanvas[0].height = myCanvas.height();
Shannimal correction
var el = $('#mycanvas');
el.attr('width', parseInt(el.css('width')))
el.attr('height', parseInt(el.css('height')))
Canvas renders image by buffer, so when you specify the width and height HTML attributes the buffer size and length changes, but when you use CSS, the buffer's size is unchanged. Making the image stretched.
Using HTML sizing.
Size of canvas is changed -> buffer size is changed -> rendered
Using CSS sizing
Size of canvas is changed -> rendered
Since the buffer length is kept unchanged, when the context renders the image,
the image is displayed in resized canvas (but rendered in unchanged buffer).
CSS sets the width and height of the canvas element so it affects the coordinate space leaving everything drawn skewed
Here's my way on how to set the width and height with Vanilla JavaScript
canvas.width = numberForWidth
canvas.height = numberForHeight
I believe CSS has much better machinery for specifying the size of the canvas and CSS must decide styling, not JavaScript or HTML. Having said that, setting width and height in HTML is important for working around the issue with canvas.
CSS has !important rule that allows to override other styling rules for the property, including those in HTML. Usually, its usage is frowned upon but here the use is a legitimate hack.
In Rust module for WebAssembly you can do the following:
fn update_buffer(canvas: &HtmlCanvasElement) {
canvas.set_width(canvas.client_width() as u32);
canvas.set_height(canvas.client_height() as u32);
}
//..
#[wasm_bindgen(start)]
pub fn start() -> Result<(), JsValue> {
// ...
let canvas: Rc<_> = document
.query_selector("canvas")
.unwrap()
.unwrap()
.dyn_into::<HtmlCanvasElement>()
.unwrap()
.into();
update_buffer(&canvas);
// ...
// create resizing handler for window
{
let on_resize = Closure::<dyn FnMut(_)>::new(move |_event: Event| {
let canvas = canvas.clone();
// ...
update_buffer(&canvas);
// ...
window.add_event_listener_with_callback("resize", on_resize.as_ref().unchecked_ref())?;
on_resize.forget();
}
}
There we update the canvas buffer once the WASM module is loaded and then whenever the window is resized. We do it by manually specifying width and height of canvas as values of clientWidth and clientHeight. Maybe there are better ways to update the buffer but I believe this solution is better than those suggested by #SamB, #CoderNaveed, #Anthony Gedeon, #Bluerain, #Ben Jackson, #Manolo, #XaviGuardia, #Russel Harkins, and #fermar because
The element is styled by CSS, not HTML.
Unlike elem.style.width & elem.style.height trick used by #Manolo or its JQuery equivalent used by #XaviGuardia, it will work for canvas whose size is specified by usage as flex or grid item.
Unlike the solution by #Russel Harkings, this also handles resizing. Though I like his answer because it is really clean and easy.
WASM is the future! Haha :D
P.S. there's a ton of .unwrap() because Rust explicitly handles possible failures.
P.P.S.
{
let on_resize = Closure::<dyn FnMut(_)>::new(move |_event: Event| {
let canvas = canvas.clone();
// ...
update_buffer(&canvas);
// ...
window.add_event_listener_with_callback("resize", on_resize.as_ref().unchecked_ref())?;
on_resize.forget();
}
can be done much cleaner with better libraries. E.g.
add_resize_handler(&window, move |e: ResizeEvent| {
let canvas = canvas.clone();
// ...
update_buffer(&canvas);
})
If you want a dynamic behaviour based on, e.g. CSS media queries, don't use canvas width and height attributes. Use CSS rules and then, before getting the canvas rendering context, assign to width and height attributes the CSS width and height styles:
var elem = document.getElementById("mycanvas");
elem.width = elem.style.width;
elem.height = elem.style.height;
var ctx1 = elem.getContext("2d");
...
I am using a grid with autoheight for row definition (I have a Editor inside, so my row can update it's height depending of the text).
My issue is, in another cell, there is a stack layout
StackLayout stackEspeceVariete = new StackLayout()
{
Children = { autoCompleteEspece, autoCompleteVariete }
};
stackEspeceVariete.Orientation = StackOrientation.Horizontal;
gridLignes.Children.Add(stackEspeceVariete);
Grid.SetRow(stackEspeceVariete, gridLignes.RowDefinitions.Count - 1);
Grid.SetColumn(stackEspeceVariete, 2);
Adding the stacklayout cause my row to take all the screen size. I want the stacklayout to take the size it's needed, not all screen size.
I tried changing the vertical option but no success.
I also tried to fix the stacklayout height to 130, it's was "working" but, the row height was no longer changing, depending on the editor text.
It's like the row is fixed to the stacklayout child
Do you have any idea ?
Thanks
I need to show the grid lines on area chart within the background. I am working on amcharts area chart. I need the chart like attachment image.
For v4, please check out our guide on Axis Ranges for Series.
Our Chart With Gaps In Data demo does exactly what's shown in your screenshot:
The parts that allow the grid lines to come through is that the fills are transparent via fillOpacity:
// There's no series.fill because it has its own color already
series.fillOpacity = 0.2;
// [...]
range.contents.stroke = chart.colors.getIndex(2);
range.contents.fill = range.contents.stroke;
range.contents.fillOpacity = 0.2;
Let us know if this helps.
You have to use gridAboveGraphs and set it to true in your chart config.
AmCharts.makeChart("chartdivcontainer", {
"gridAboveGraphs": true
});
I have a layout that has sum specifications when it is in portrait. But when I change the screen orientation the layout needs to reorganize to fit the entire screen. The problem is that the layout keeps he's dimensions. So if the layout starts portrait the I change to landscape the layout keeps the portrait configuration. How can I make my layout so it auto reorganizes on screen orientation changes?
How I create my views:
var deviceHeight = Ti.Platform.displayCaps.platformHeight,
deviceWidth = Ti.Platform.displayCaps.platformWidth,
platform = Ti.Platform.osname;
if (platform == 'android') {
deviceHeight = Math.round(Ti.Platform.displayCaps.platformHeight / Ti.Platform.displayCaps.logicalDensityFactor);
deviceWidth = Math.round(Ti.Platform.displayCaps.platformWidth / Ti.Platform.displayCaps.logicalDensityFactor);
}
var View = Ti.UI.createView({
height : deviceHeight,
width : deviceWidth,
backgroundColor : 'white',
layout : 'vertical'
});
Very important: Don't specify width in points/pixels, but in percentages. Or use relative width. For example, if you want a view that is full width, minus 10 left and 10 right, specify that:
Ti.UI.createView(){
left: 10,
right: 10
}
Treat Apps different as websites! Make everything relative. There are so many resolutions it is impossible to make a layout PER resolution. Make a single solution for mobile, and possible re-arrange some stuff for tablets.
If you really want to redraw manually, use this event and redefine all your views after again:
Ti.Gesture.addEventListener('orientationchange',function(e) {
});
For this to work, you need to keep a reference to all your views and adjust where you like.
I am facing a problem with the Kendo Grid width. I want the grid to stretch to fit the content of the grid. This grid which I am working on is created dynamically, so at times it may have just 2 columns and at times it may have max 5 columns. I don't want the grid to expand and take the whole page for showing just two columns.
To get this working I added the following css
.k-grid table{
display: inline;
}
The problem is that when this style is applied, it completely messes up the column header and column alignment. Does anyone know how to fix this?
Actually this is really simple. But I wasted lot of time cause I did not get the correct source. You just need to implement following things.
Make the grid sortable: false
and use this CSS
#gridId table {
width: auto;
}
But with this you loose the scrolling feature. But you can wrap your kendo grid in another container and implement your own scrolling.
var grid = $("#kendoGridName");
grid.width(400);
Rather than trying to apply some css you could use some jQuery to perform this task. I do something similar in terms of height. So maybe something like this would work for you (I have modified this to do height and width).
function resizeGrid(size) {
if (size === null || size === undefined) {
size = 0.6;
}
var windowHeight = $(window).height();
var windowWidth = $(window).width();
windowHeight = windowHeight * size;
windowWidth = windowWidth * size;
$(".k-grid-content").height(windowHeight)
$(".k-grid).width(windowWidth);
}
so all this function does is scale the grid based on the current window size so for example if you want the grid to take up all the available space ie max height and width you would call resizeGrid(1) if you wanted it smaller say to take 50% of the screen size then you would use reszieGrid(0.5) if no value is used then the function just goes with a default of 60% of the available width/height.
so you could call this after your initialization of the grid and then scale the grid to an appropriate size.
by targeting the kendo css classes it makes this function easier to reuse.
if you need more info let me know.