snapshot: a new debug tool

I might have finally hit on the right approach: a hotkey that dumps
information. Doesn't swamp me with data, and also doesn't perturb
anything.

y_of_schema1 returns consistent results as I pan around.
I'm just not actually printing the lines at that y. I'm printing it at
that y/Viewport.zoom.

What might be confusing here is that I started out with a simple mental
model:
  * perform computations in surface coordinates (sx,sy)
  * render in viewport coordinates (vx,vy)

But for text quality reasons I need to perform many computations in
"scaled surface" coordinates.

Viewport coordinates are both offset and scaled relative to surface
coordinates. Scaled surface = just scaled relative to surface, not
offset.

I don't have a clear mental model here for when to use this.

I did already use it in one place with my simple mental model: you have
to scale distances like rect.w and rect.h but it's incorrect to offset
them. Maybe I'm getting this wrong somehow.

0023-on.keychord_press

@@ -14,6 +14,8 @@ on.keychord_press = function(chord, key)
 		-- reset zoom
 		Viewport.zoom = 1.0
 		A()
+	elseif chord == 'C-z' then
+		dump_state()
 	elseif Cursor_node and Cursor_node.editor.cursor_x then
 		local old_top = {line=Cursor_node.editor.screen_top1.line, pos=Cursor_node.editor.screen_top1.pos}
 		edit.keychord_press(Cursor_node.editor, chord, key)
@@ -54,4 +56,4 @@ on.keychord_press = function(chord, key)
 			B()
 		end
 	end
-end
+end

0030-update_editor_box

@@ -8,11 +8,10 @@ update_editor_box = function(node)
 		node.editor.top = vy(node.y)
 	else
 		node.editor.screen_top1, node.editor.top = schema1_of_y(node.editor, Viewport.y-node.y)
-		print('update', Viewport.y-node.y+node.editor.top - y_of_schema1(node.editor, node.editor.screen_top1))
 	end
 	node.editor.left = math.floor(vx(node.x))
 	node.editor.right = math.ceil(vx(node.x+node.w))
 	node.editor.width = node.editor.right - node.editor.left
 	edit.update_font_settings(node.editor, scale(20))
 	Text.redraw_all(node.editor)
-end
+end

0034-dump_state

@@ -0,0 +1,10 @@
+dump_state = function()
+	print('===')
+	print('zoom', Viewport.zoom)
+	print('viewport', Viewport.y)
+	print('node', Page.data[1].y)
+	print('node renders from', Page.data[1].editor.top)
+	print('screen top', Page.data[1].editor.screen_top1.line)
+	local l = 25
+	print('y of line', l, y_of_schema1(Page.data[1].editor, {line=l, pos=1}))
+end