93 lines
3.3 KiB
Python
93 lines
3.3 KiB
Python
# Copyright (C) 2006, Red Hat, Inc.
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#
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# This library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2 of the License, or (at your option) any later version.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with this library; if not, write to the
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# Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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# Boston, MA 02111-1307, USA.
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""" Units conversions and constants
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The purpose of the module is to keep Sugar independent from the
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screen size, factory and DPI. There a few use cases that needs
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to be considered:
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- The XO display. The screen DPI is 201 and the screen
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resolution is 1200x900. The screen factor is 4:3.
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- The Sugar emulator runned on traditional screens. Resolution
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is variable, ranging from 800x600 up to 1200x900. The DPI
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is usually but not necessarily 96. The screen factor is
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either 4:3 or 16:9
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- Other embedded devices. DPI, screen resolution and screen
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factor are variable.
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To achieve the goal a few rules needs to be respected when
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writing code for Sugar:
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- Never use absolute positioning. Use the layout facilities
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provided by HippoCanvas. If you need custom layouts make
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sure they adapt to different screen resolutions.
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- Never specify sizes, fonts, borders or padding using pixels.
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Instead use the device independt units provided by this
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module.
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We are currently providing the following resolution independent
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units:
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- Points.
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- Grid. One cell of the screen grid as specificed by the HIG.
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- Microgrid. One microcell of the screen grid as
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specificed by the HIG.
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- A set of icon sizes as specified by the HIG (standard, small,
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medium, large, xlarge).
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Just scaling UI elements on the base of the screen DPI is not
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enough to provide a good experience. For example on smaller
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screens smaller fonts or icons might be acceptable to gain
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screen aestate. For this reason a constant zoom factor is
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applied to all the transformation from resolution independent
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units to device units.
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"""
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import gtk
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import _sugar
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_MAX_ZOOM_FACTOR = 1.5
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_ZOOM_CONSTANT = 600.0
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def _compute_zoom_factor():
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screen_width = gtk.gdk.screen_width()
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if _sugar.get_screen_dpi() == 201.0 and screen_width == 1200:
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return 1.0
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else:
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return min(_MAX_ZOOM_FACTOR, screen_width / _ZOOM_CONSTANT)
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_dpi_factor = float(_sugar.get_screen_dpi()) / 201.0
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_zoom_factor = _compute_zoom_factor()
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STANDARD_ICON_SCALE = 1.0 * _dpi_factor * _zoom_factor
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SMALL_ICON_SCALE = 0.5 * _dpi_factor * _zoom_factor
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MEDIUM_ICON_SCALE = 1.5 * _dpi_factor * _zoom_factor
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LARGE_ICON_SCALE = 2.0 * _dpi_factor * _zoom_factor
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XLARGE_ICON_SCALE = 3.0 * _dpi_factor * _zoom_factor
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def points_to_pixels(points):
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return int(points * _zoom_factor)
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def grid_to_pixels(units):
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return int(units * 75.0 * _dpi_factor * _zoom_factor)
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def microgrid_to_pixels(units):
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return int(units * 15.0 * _dpi_factor * _zoom_factor)
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