Changes between Version 6 and Version 7 of ScalesAndZooms


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Timestamp:
Jun 6, 2012 3:55:28 PM (10 years ago)
Author:
jamesr@google.com
Comment:

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  • ScalesAndZooms

    v6 v7  
    1414 * Physical pixel - represents one unit of display on the physical display.  Also known as device-dependent pixel.
    1515 * CSS viewport - dimensions of the CSS initial containing block, in CSS pixels.
    16  * Virtual viewport - visible region of the screen when using zoom gestures. [measured in which pixel units?]
    17  * Physical viewport - dimensions of the physical display, in physical pixels.
     16 * Virtual viewport - visible region of the screen when using zoom gestures, measured in logical pixels.
    1817
    1918= Types of scales and zooms =
     
    2928
    3029== Device scale ==
    31 Device scale is a property of the physical display that the web content is being rendered into.  This could be a monitor, projector, print media, etc.  The device scale can change for a given Page, for instance if the window containing the Page is moved to a different monitor or if the user switches from using a monitor to using a projector.  The device scale typically does not change as a result of the user interacting with the web page.  When the device scale changes, a browser implementation may wish to re-rasterize the content at the new scale in order to render content more sharply.  The size of the viewport and the layout of the page do not change if the device scale factor changes.  Web pages may use window.devicePixelRatio and CSS media queries to provide different content, such as higher-resolution image assets, for high-DPI devices.
     30Device scale is a property of the physical display that the web content is being rendered into.  This could be a monitor, projector, print media, etc.  The device scale can change for a given Page, for instance if the window containing the Page is moved to a different monitor or if the user switches from using a monitor to using a projector.  The device scale typically does not change as a result of the user interacting with the web page.  When the device scale changes, a browser implementation may wish to re-rasterize vector content and resample bitmap content at the new scale in order to render content more sharply.  The size of the viewport and the layout of the page do not change if the device scale factor changes.  Web pages may use window.devicePixelRatio and CSS media queries to provide different content, such as higher-resolution image assets, for high-DPI devices.
    3231
    3332== Page scale ==
     
    4241== CSS / SVG scale transforms ==
    4342
    44 CSS and SVG both expose transform functionality that can cause parts of the page to be scaled.
     43CSS and SVG both expose transform functionality that can cause parts of the page to be scaled.  This could be either an explicit scale transform or a more complicated transformation that includes scaling.  This changes the local coordinate space for part of the DOM.