A new custom tool¶
This example shows a custom GestureTool subclass that can be used to sketch on the plot canvas by dragging a mouse (or finger on a touch device).
from bokeh.core.properties import Instance
from bokeh.io import output_file, show
from bokeh.models import ColumnDataSource, Tool
from bokeh.plotting import figure
from bokeh.util.compiler import TypeScript
output_file('tool.html')
TS_CODE = """
import {GestureTool, GestureToolView} from "models/tools/gestures/gesture_tool"
import {ColumnDataSource} from "models/sources/column_data_source"
import {PanEvent} from "core/ui_events"
import * as p from "core/properties"
export class DrawToolView extends GestureToolView {
model: DrawTool
//this is executed when the pan/drag event starts
_pan_start(_ev: PanEvent): void {
this.model.source.data = {x: [], y: []}
}
//this is executed on subsequent mouse/touch moves
_pan(ev: PanEvent): void {
const {frame} = this.plot_view
const {sx, sy} = ev
if (!frame.bbox.contains(sx, sy))
return
const x = frame.x_scale.invert(sx)
const y = frame.y_scale.invert(sy)
const {source} = this.model
source.get_array("x").push(x)
source.get_array("y").push(y)
source.change.emit()
}
// this is executed then the pan/drag ends
_pan_end(_ev: PanEvent): void {}
}
export namespace DrawTool {
export type Attrs = p.AttrsOf<Props>
export type Props = GestureTool.Props & {
source: p.Property<ColumnDataSource>
}
}
export interface DrawTool extends DrawTool.Attrs {}
export class DrawTool extends GestureTool {
properties: DrawTool.Props
__view_type__: DrawToolView
constructor(attrs?: Partial<DrawTool.Attrs>) {
super(attrs)
}
tool_name = "Drag Span"
icon = "bk-tool-icon-lasso-select"
event_type = "pan" as "pan"
default_order = 12
static {
this.prototype.default_view = DrawToolView
this.define<DrawTool.Props>(({Ref}) => ({
source: [ Ref(ColumnDataSource) ],
}))
}
}
"""
class DrawTool(Tool):
__implementation__ = TypeScript(TS_CODE)
source = Instance(ColumnDataSource)
source = ColumnDataSource(data=dict(x=[], y=[]))
plot = figure(x_range=(0, 10), y_range=(0, 10), tools=[DrawTool(source=source)])
plot.title.text = "Drag to draw on the plot"
plot.line('x', 'y', source=source)
show(plot)