Fix z range which sometimes caused the last stroke to have Z equal to

exactly 1 and thus not draw. Fix wrong size of texture upload

client/webgl_draw.js

@@ -61,7 +61,7 @@ function upload_square_rgba16ui_texture(gl, serializer, texture_size) {
     // Upload last row
     if (last_row > 0) {  
         const last_row_upload = last_row * bpp;
-        gl.texSubImage2D(gl.TEXTURE_2D, 0, 0, rows_uploaded, last_row, 1, gl.RGBA_INTEGER, gl.UNSIGNED_SHORT, new Uint16Array(serializer.buffer, whole_upload, last_row_upload * 4));
+        gl.texSubImage2D(gl.TEXTURE_2D, 0, 0, rows_uploaded, last_row, 1, gl.RGBA_INTEGER, gl.UNSIGNED_SHORT, new Uint16Array(serializer.buffer, whole_upload, last_row_upload));
     }
 
     serializer.gpu_upload_from = serializer.offset;

client/webgl_shaders.js

@@ -68,7 +68,7 @@ const sdf_vs_src = `#version 300 es
             screen02 += vec2(100.0); // shift offscreen
         }
 
-        gl_Position = vec4(screen02 - 1.0, (float(stroke_index + 1) / float(u_stroke_count)) * 2.0 - 1.0, 1.0);
+        gl_Position = vec4(screen02 - 1.0, (float(stroke_index + 1) / float(u_stroke_count + 1)) * 2.0 - 1.0, 1.0);
     }
 `;