Changes between Initial Version and Version 1 of Ticket #12350, comment 14


Ignore:
Timestamp:
2016-02-17T08:37:03+01:00 (5 years ago)
Author:
kolesar
Comment:

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  • Ticket #12350, comment 14

    initial v1  
    33> @kolesar: what's the status? Can we help?
    44
    5 The only missing piece is zoom slider at top left corner. It has a range from 35 to 150, unit of this number is not well defined. It is a logaritmic value of scale with base 1.1 (!) where calculation does not use logarithm function but a loop that repeatedly divides a number with 1.1, see `MapSlider.propertyChange` method.
     5The only missing piece is zoom slider at top left corner. It has a range from 35 to 150, unit of this number is not well defined. It divides screen extents with world extents then converts to a logaritmic value with base 1.1 (!) where calculation does not use logarithm function but a loop that repeatedly divides a number with 1.1, see `MapSlider.propertyChange` method.
    66
    7 Zooming does define maximum `zoom` in meters/pixels (1 cm == 100 px) but this unit can't be represented in `scale` (EastNorth/pixel) for the whole area of projection because meters/pixels (or meters/EastNorth) varies in some projections, including EPSG:3857 Spherical Mercator. In this projection EastNorth unit equals to a meters only at Equator. Moving towards North or South one EasthNort unit means less than a meter.
     7This calculation makes displayed value depending on window size. It you only resize JOSM window and then zoom in and back to original zoom, you will get a different number here. Strange, isn't it?
     8
     9JOSM defines maximum `zoom` in meters/pixels (1 cm == 100 px) but this unit can't be represented in `scale` (EastNorth/pixel) for the whole area of projection because meters/pixels (or meters/EastNorth) varies in some projections, including EPSG:3857 Spherical Mercator. In this projection EastNorth unit equals to a meters only at Equator. Moving towards North or South one EasthNort unit means less than a meter.
    810
    911Projections do not have a method to give maximum of this unit. JOSM currently uses a different way to limit zoom: checks meters/pixels at the current viewport center and if it's too large, then forces this limit calculated for the current place. See `NavigatableComponent.zoomTo`.
     
    1517This control can be adjusted with keyboard. When focused, keys right and left adjust one step (integer value plus/minus). Step with 1.1 based logaritm was too small to step to 2x zoom change, snapping moved this slider back to original position, zoom did not change. That's why I have modified this control.
    1618
    17 Definitions like 'minimum zoom', 'maximum zoom', 'whole world', 'meters/pixels' vary from projection to another and also for different places of the world.
     19Definitions like 'minimum zoom', 'maximum zoom', 'world extents', 'meters/pixels' vary from projection to another and also for different places of the world.
    1820
    1921Question: can we discuss this topic here or can I leave this control as it is?