chromium/pdf/pdf_ink_transform.h

// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef PDF_PDF_INK_TRANSFORM_H_
#define PDF_PDF_INK_TRANSFORM_H_

#include "pdf/buildflags.h"
#include "pdf/ink/ink_affine_transform.h"
#include "pdf/page_orientation.h"
#include "ui/gfx/geometry/point_f.h"

static_assert …;

namespace gfx {
class Rect;
class Vector2dF;
}  // namespace gfx

namespace chrome_pdf {

// Converts a screen-based event input position into a page-based CSS pixels
// position.  This canonical format is relative to the upper-left corner of a
// page for its original orientation at a scale factor of 100%.
// - `event_position`:
//     The input position, in screen-based coordinates.  Must already have had
//     any offset from a viewport origin to the page origin applied to it.
// - `orientation`:
//     Current orientation of the page.
// - `page_content_rect`:
//     Scaled and rotated CSS coordinates of the page content area.  The amount
//     of scale and rotation match that of `orientation` and `scale_factor`.
//     The area's origin has the same offset from a viewport origin as
//     `event_position`.  Must not be empty.
// - `scale_factor`:
//     The current zoom factor, with 1.0 representing identity.  Must be greater
//     than zero.  This is used to ensure the resulting point is relative to a
//     scale factor of 100%.
gfx::PointF EventPositionToCanonicalPosition(const gfx::PointF& event_position,
                                             PageOrientation orientation,
                                             const gfx::Rect& page_content_rect,
                                             float scale_factor);

// Generate the affine transformation for rendering a page's strokes to the
// screen, based on the page and its position within the viewport.  Parameters
// are the same as for `EventPositionToCanonicalPosition()`, with the addition
// of:
// - `viewport_origin_offset`:
//     The offset within the rendering viewport to where the page images will
//     be drawn.  Since the offset is a location within the viewport, it must
//     always contain non-negative values.  Values are scaled CSS coordinates,
//     where the amount of scaling matches that of `scale_factor`.
//
//     The X value in the offset repesents an unused area in the viewport to
//     the left of the pages, where no page pixels will be drawn.  This can
//     happen when the viewport is wider than the width of the rendered pages
//     and the pages are centered within the viewport.
//     The Y value in the offset similarly represents an unused area at the
//     top of the viewport where no page pixels would be rendered.
//
//     If the document scrolls vertically, then centering pages horizontally
//     within the viewport would lead to an offset whose X value is between
//     zero and less than half the viewport width.  The Y-offset value is
//     likely zero or a very small number for any viewport boundary padding.
//     If the document scrolls horizontally, then the reasoning of expected X
//     and Y values for the offset would be reversed.
//
//     Conceptually, the viewport origin offset is at X in this diagram, for a
//     document whose pages scroll vertically and a viewport that doesn't
//     bother with any vertical padding:
//
//                       +-------------+ +------------+         ^   scroll
//                       | page N      | | page N+1   |        /|\  direction
//                       |             | |            |         |
//                       |             | |            |         |
//                       |             | |            |
//     +-----------------X-------------+-+------------+-----------------+
//     | viewport        |             | |            |                 |
//     |                 |             | |            |                 |
//     |                 +------------ + +------------+                 |
//     |                                                                |
//     |                 +------------ + +------------+                 |
//     |                 | page N+2    | | page N+3   |                 |
//     |                 |             | |            |                 |
//     |                 |             | |            |                 |
//     |                 |             | |            |                 |
//     |                 |             | |            |                 |
//     +-----------------+-------------+-+------------+-----------------+
//                       |             | |            +
//                       +-------------+ +------------+
//
InkAffineTransform GetInkRenderTransform(
    const gfx::Vector2dF& viewport_origin_offset,
    PageOrientation orientation,
    const gfx::Rect& page_content_rect,
    float scale_factor);

}  // namespace chrome_pdf

#endif  // PDF_PDF_INK_TRANSFORM_H_