1 // Copyright 2014 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef CHROME_BROWSER_CHROMEOS_UI_ACCESSIBILITY_FOCUS_RING_H_ 6 #define CHROME_BROWSER_CHROMEOS_UI_ACCESSIBILITY_FOCUS_RING_H_ 7 8 #include "ui/gfx/point.h" 9 #include "ui/gfx/rect.h" 10 11 namespace chromeos { 12 13 // An AccessibilityFocusRing is a special type of shape designed to 14 // outline the focused object on the screen for users with visual 15 // impairments. It's specifically designed to outline text ranges that 16 // span multiple lines (we'll call this a "paragraph" shape from here on, 17 // but it works for any text range), so it can outline a shape defined by a 18 // few words from the first line, the complete contents of more lines, 19 // followed by a few words from the last line. See the figure below. 20 // When highlighting any other object, it outlines a rectangular shape. 21 // 22 // The outline is outset from the object it's highlighting by a few pixels; 23 // this margin distance also determines its border radius for rounded 24 // corners. 25 // 26 // An AccessibilityFocusRing can be initialized with either a rectangle 27 // defining the bounds of an object, or a paragraph-shape with three 28 // rectangles defining a top line, a body, and a bottom line, which are 29 // assumed to be adjacent to one another. 30 // 31 // Initializing an AccessibilityFocusRing computes the following 36 points 32 // that completely define the shape's outline. This shape can be traced 33 // using Skia or any other drawing utility just by drawing alternating 34 // straight lines and quadratic curves (e.g. a line from 0 to 1, a curve 35 // from 1 to 3 with 2 as a control point, then a line from 3 to 4, and so on. 36 // 37 // The same path should be used even if the focus ring was initialized with 38 // a rectangle and not a paragraph shape - this makes it possible to 39 // smoothly animate between one object and the next simply by interpolating 40 // points. 41 // 42 // Noncontiguous shapes should be handled by drawing multiple focus rings. 43 // 44 // The 36 points are defined as follows: 45 // 46 // 2 3------------------------------4 5 47 // / | 48 // 1 6 49 // | First line of paragraph | 50 // 0 7 51 // / | 52 // 32 33-34 35 8 9---------------10 11 53 // / | 54 // 31 Middle line of paragraph.......................... 12 55 // | | 56 // | | 57 // | Middle line of paragraph.......................... | 58 // | | 59 // | | 60 // 30 Middle line of paragraph.......................... 13 61 // | | 62 // 29 28---------27 26 17 16---------15 14 63 // | | 64 // 25 18 65 // | Last line of paragraph | 66 // 24 19 67 // | | 68 // 23 22-----------------------21 20 69 70 struct AccessibilityFocusRing { 71 // Construct an AccessibilityFocusRing that outlines a rectangular object. 72 static AccessibilityFocusRing CreateWithRect( 73 const gfx::Rect& bounds, int margin); 74 75 // Returns a ring where 0.0 returns r1, 1.0 returns r2, and any number 76 // in-between interpolates linearly between them. 77 static AccessibilityFocusRing Interpolate( 78 const AccessibilityFocusRing& r1, 79 const AccessibilityFocusRing& r2, 80 double fraction); 81 82 // Construct an AccessibilityFocusRing that outlines a paragraph-shaped 83 // object. 84 static AccessibilityFocusRing CreateWithParagraphShape( 85 const gfx::Rect& top_line, 86 const gfx::Rect& body, 87 const gfx::Rect& bottom_line, 88 int margin); 89 90 gfx::Rect GetBounds() const; 91 92 gfx::Point points[36]; 93 }; 94 95 } // namespace chromeos 96 97 #endif // CHROME_BROWSER_CHROMEOS_UI_ACCESSIBILITY_FOCUS_RING_H_ 98
