------------------------------------------------------------------------------
--                                                                          --
--                              DEMO CANVAS                                 --
--                                                                          --
--                            LOGICAL PIXELS                                --
--                                                                          --
--                               S p e c                                    --
--                                                                          --
-- Copyright (C) 2024                                                       --
-- Mario Blunk / Blunk electronic                                           --
-- Buchfinkenweg 3 / 99097 Erfurt / Germany                                 --
--                                                                          --
-- This library is free software;  you can redistribute it and/or modify it --
-- under terms of the  GNU General Public License  as published by the Free --
-- Software  Foundation;  either version 3,  or (at your  option) any later --
-- version. This library is distributed in the hope that it will be useful, --
-- but WITHOUT ANY WARRANTY;  without even the implied warranty of MERCHAN- --
-- TABILITY or FITNESS FOR A PARTICULAR PURPOSE.                            --
--                                                                          --
-- You should have received a copy of the GNU General Public License and    --
-- a copy of the GCC Runtime Library Exception along with this program;     --
-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
-- <http://www.gnu.org/licenses/>.                                          --
------------------------------------------------------------------------------

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--   The two letters "CS" indicate a "construction site" where things are not
--   finished yet or intended for the future.

--   Please send your questions and comments to:
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--

with glib;

package demo_logical_pixels is

	-- GTK3 uses the type gdouble for primitive draw operations
	-- on the canvas. It also uses gdouble for scrollbar settings.
	-- A point, a vector or a distance is expressed in
	-- so called "logical pixels".	

	-- We derive a new type from glib.gdouble in order to 
	-- get a clear separation from things defined in glib:
	type type_logical_pixels is new glib.gdouble;


	-- Converts logical pixels to a human readable string:
	function to_string (
		lp : in type_logical_pixels)
		return string;
	
	
	-- This function converts a gdouble number
	-- to logical pixels:
	function to_lp (
		gd : in glib.gdouble)
		return type_logical_pixels;

	
	-- This function converts logical pixels
	-- to a gdouble number:
	function to_gdouble (
		lp : in type_logical_pixels)
		return glib.gdouble;

	
	-- Use this type for distances, lengths, scrollbar settings, 
	-- primitive draw operations, ...
	-- because such things are always positive numbers:
	subtype type_logical_pixels_positive is type_logical_pixels
		range 0.0 .. type_logical_pixels'last;

	
	-- This function converts positive logical pixels
	-- to a positive gdouble number:
	function to_gdouble_positive (
		lp : in type_logical_pixels_positive)
		return glib.gdouble;

	
	-- A point, a location vector or a distance vector is
	-- defined by this type:
	type type_logical_pixels_vector is record
		x, y : type_logical_pixels := 0.0;
	end record;


	-- This function outputs the x and y component of a vector
	-- on the console:
	function to_string (
		v : in type_logical_pixels_vector)
		return string;



	
	-- Clips the given value by the given limit.
	-- If the given value is less or equal the limit,
	-- then value remains unchanged:
	procedure clip_max (
		value	: in out type_logical_pixels;
		limit	: in type_logical_pixels);
	
	-- Clips the given value by the given limit.
	-- If the given value is greater or equal the limit,
	-- then value remains unchanged:
	procedure clip_min (
		value	: in out type_logical_pixels;
		limit	: in type_logical_pixels);
	
	
end demo_logical_pixels;

