charts: initial import

authors.txt

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+Alexander Ilin

charts.factor

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+! Copyright (C) 2016-2017 Alexander Ilin.
+
+USING: accessors colors.constants kernel math opengl opengl.gl
+sequences specialized-arrays.instances.alien.c-types.float
+ui.gadgets ui.render ;
+IN: charts
+
+TUPLE: chart < gadget ;
+
+! Data must be sorted by ascending x coordinate.
+TUPLE: line < gadget color data ;
+
+M: chart pref-dim* drop { 300 300 } ;
+
+: (line-vertices) ( seq -- vertices )
+    concat [ 0.3 + ] float-array{ } map-as ;
+
+: draw-line ( seq -- )
+    dup dup length odd? [ [ 1 head* ] dip ] [ 1 head* ] if
+    1 tail append
+    [ (line-vertices) gl-vertex-pointer GL_LINES 0 ] keep
+    length glDrawArrays ;
+
+! Return the bottom-left and top-right corners of the visible area.
+: chart-axes ( chart -- seq )
+    drop { { 0 300 } { 300 0 } } ;
+
+! There are several things to do to present data on the screen.
+! Map the data coordinates to the screen coordinates.
+! Cut off data outside the presentation window.
+! Remove redundant points from the drawing pass.
+
+M: line draw-gadget*
+    dup parent>> dup chart? [
+        chart-axes drop
+        [ color>> gl-color ]
+        [ data>> draw-line ] bi
+    ] [ 2drop ] if ;
+
+! chart new line new COLOR: blue >>color { { 0 100 } { 100 0 } { 100 50 } { 150 50 } { 200 100 } } >>data add-gadget gadget.