fix pressure spacing, blend mode preview

src/node_canvas.cpp

@@ -20,6 +20,8 @@ void NodeCanvas::init()
     m_sampler.create();
     m_sampler.set_filter(GL_LINEAR, GL_NEAREST);
     
+    m_sampler_nearest.create(GL_NEAREST);
+    
     m_sampler_linear.create(GL_LINEAR);
     m_sampler_stencil.create(GL_LINEAR, GL_REPEAT);
     m_face_plane.create<1>(2, 2);
@@ -493,7 +495,7 @@ void NodeCanvas::draw()
         glViewport(c.x + App::I.off_x, c.y + App::I.off_y, c.z, c.w);
 
         // draw the canvas
-        m_sampler_linear.bind(0);
+        m_sampler_nearest.bind(0);
         glActiveTexture(GL_TEXTURE0);
         m_rtt.bindTexture();
         ShaderManager::use(kShader::Texture);