STR:

1. Enable gfx.webrender.all.
2. Slowly type a lot of characters in a textarea such as Bugzilla's comment box or Slack's message box.
3. Watch the text input caret as you type.

RESULT:
About every 10-20 characters, the caret appears to jump back about 4-5 characters and those characters will flash. The flashing text is easier to detect if you zoom the page 300%.

If I disable WebRender, the problem goes away. I first noticed this problem today, so I assumed it was either a regression in Firefox 67.0a1 (2019-03-04) or in the Windows 10 Insider Preview update (build 18342.19h1_release.190215-1528) that Microsoft released yesterday. I tried to bisect this bug using mozregression, but the problem goes back at least until 2018-09-29, so this might be a Windows 10 Insider Preview problem.

Here is the Graphics section from my about:support:

Application Basics

Name: Firefox
Version: 67.0a1
Build ID: 20190304093752
Update Channel: nightly
User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:67.0) Gecko/20100101 Firefox/67.0
OS: Windows_NT 10.0
Launcher Process: Enabled
Multiprocess Windows: 6/6 Enabled by default
Web Content Processes: 10/8
Enterprise Policies: Inactive
Google Key: Found
Mozilla Location Service Key: Found
Safe Mode: false

Graphics

Features
Compositing: WebRender
asyncPanZoom: wheel input enabled; touch input enabled; scrollbar drag enabled; keyboard enabled; autoscroll enabled
webgl1WSIInfo: EGL_VENDOR: Google Inc. (adapter LUID: 000000000000e9ad) EGL_VERSION: 1.4 (ANGLE 2.1.0.eff6bfdb1db9) EGL_EXTENSIONS: EGL_EXT_create_context_robustness EGL_ANGLE_d3d_share_handle_client_buffer EGL_ANGLE_d3d_texture_client_buffer EGL_ANGLE_surface_d3d_texture_2d_share_handle EGL_ANGLE_query_surface_pointer EGL_ANGLE_window_fixed_size EGL_ANGLE_keyed_mutex EGL_ANGLE_surface_orientation EGL_ANGLE_direct_composition EGL_NV_post_sub_buffer EGL_KHR_create_context EGL_EXT_device_query EGL_KHR_image EGL_KHR_image_base EGL_KHR_gl_texture_2D_image EGL_KHR_gl_texture_cubemap_image EGL_KHR_gl_renderbuffer_image EGL_KHR_get_all_proc_addresses EGL_KHR_stream EGL_KHR_stream_consumer_gltexture EGL_NV_stream_consumer_gltexture_yuv EGL_ANGLE_flexible_surface_compatibility EGL_ANGLE_stream_producer_d3d_texture EGL_ANGLE_create_context_webgl_compatibility EGL_CHROMIUM_create_context_bind_generates_resource EGL_CHROMIUM_sync_control EGL_EXT_pixel_format_float EGL_KHR_surfaceless_context EGL_ANGLE_display_texture_share_group EGL_ANGLE_create_context_client_arrays EGL_ANGLE_program_cache_control EGL_ANGLE_robust_resource_initialization EGL_ANGLE_create_context_extensions_enabled EGL_MOZ_create_context_provoking_vertex_dont_care EGL_EXTENSIONS(nullptr): EGL_EXT_client_extensions EGL_EXT_platform_base EGL_EXT_platform_device EGL_ANGLE_platform_angle EGL_ANGLE_platform_angle_d3d EGL_ANGLE_device_creation EGL_ANGLE_device_creation_d3d11 EGL_ANGLE_experimental_present_path EGL_KHR_client_get_all_proc_addresses EGL_KHR_debug EGL_ANGLE_explicit_context
WebGL 1 Driver Renderer: Google Inc. -- ANGLE (Intel(R) UHD Graphics 630 Direct3D11 vs_5_0 ps_5_0)
WebGL 1 Driver Version: OpenGL ES 2.0 (ANGLE 2.1.0.eff6bfdb1db9)
WebGL 1 Driver Extensions: GL_ANGLE_client_arrays GL_ANGLE_depth_texture GL_ANGLE_explicit_context GL_ANGLE_explicit_context_gles1 GL_ANGLE_framebuffer_blit GL_ANGLE_framebuffer_multisample GL_ANGLE_instanced_arrays GL_ANGLE_lossy_etc_decode GL_ANGLE_pack_reverse_row_order GL_ANGLE_program_cache_control GL_ANGLE_request_extension GL_ANGLE_robust_client_memory GL_ANGLE_texture_compression_dxt3 GL_ANGLE_texture_compression_dxt5 GL_ANGLE_texture_usage GL_ANGLE_translated_shader_source GL_CHROMIUM_bind_generates_resource GL_CHROMIUM_bind_uniform_location GL_CHROMIUM_color_buffer_float_rgb GL_CHROMIUM_color_buffer_float_rgba GL_CHROMIUM_copy_compressed_texture GL_CHROMIUM_copy_texture GL_CHROMIUM_sync_query GL_EXT_blend_minmax GL_EXT_color_buffer_half_float GL_EXT_debug_marker GL_EXT_discard_framebuffer GL_EXT_disjoint_timer_query GL_EXT_draw_buffers GL_EXT_frag_depth GL_EXT_map_buffer_range GL_EXT_occlusion_query_boolean GL_EXT_read_format_bgra GL_EXT_robustness GL_EXT_sRGB GL_EXT_shader_texture_lod GL_EXT_texture_compression_dxt1 GL_EXT_texture_compression_s3tc_srgb GL_EXT_texture_filter_anisotropic GL_EXT_texture_format_BGRA8888 GL_EXT_texture_rg GL_EXT_texture_storage GL_EXT_unpack_subimage GL_KHR_debug GL_KHR_parallel_shader_compile GL_KHR_robust_buffer_access_behavior GL_NV_EGL_stream_consumer_external GL_NV_fence GL_NV_pack_subimage GL_NV_pixel_buffer_object GL_OES_EGL_image GL_OES_EGL_image_external GL_OES_compressed_ETC1_RGB8_texture GL_OES_depth32 GL_OES_element_index_uint GL_OES_get_program_binary GL_OES_mapbuffer GL_OES_packed_depth_stencil GL_OES_rgb8_rgba8 GL_OES_standard_derivatives GL_OES_surfaceless_context GL_OES_texture_float GL_OES_texture_float_linear GL_OES_texture_half_float GL_OES_texture_half_float_linear GL_OES_texture_npot GL_OES_vertex_array_object OES_compressed_EAC_R11_signed_texture OES_compressed_EAC_R11_unsigned_texture OES_compressed_EAC_RG11_signed_texture OES_compressed_EAC_RG11_unsigned_texture OES_compressed_ETC2_RGB8_texture OES_compressed_ETC2_RGBA8_texture OES_compressed_ETC2_punchthroughA_RGBA8_texture OES_compressed_ETC2_punchthroughA_sRGB8_alpha_texture OES_compressed_ETC2_sRGB8_alpha8_texture OES_compressed_ETC2_sRGB8_texture
WebGL 1 Extensions: ANGLE_instanced_arrays EXT_blend_minmax EXT_color_buffer_half_float EXT_disjoint_timer_query EXT_frag_depth EXT_shader_texture_lod EXT_sRGB EXT_texture_filter_anisotropic OES_element_index_uint OES_standard_derivatives OES_texture_float OES_texture_float_linear OES_texture_half_float OES_texture_half_float_linear OES_vertex_array_object WEBGL_color_buffer_float WEBGL_compressed_texture_s3tc WEBGL_compressed_texture_s3tc_srgb WEBGL_debug_renderer_info WEBGL_debug_shaders WEBGL_depth_texture WEBGL_draw_buffers WEBGL_lose_context
WebGL 2 Driver WSI Info: EGL_VENDOR: Google Inc. (adapter LUID: 000000000000e9ad) EGL_VERSION: 1.4 (ANGLE 2.1.0.eff6bfdb1db9) EGL_EXTENSIONS: EGL_EXT_create_context_robustness EGL_ANGLE_d3d_share_handle_client_buffer EGL_ANGLE_d3d_texture_client_buffer EGL_ANGLE_surface_d3d_texture_2d_share_handle EGL_ANGLE_query_surface_pointer EGL_ANGLE_window_fixed_size EGL_ANGLE_keyed_mutex EGL_ANGLE_surface_orientation EGL_ANGLE_direct_composition EGL_NV_post_sub_buffer EGL_KHR_create_context EGL_EXT_device_query EGL_KHR_image EGL_KHR_image_base EGL_KHR_gl_texture_2D_image EGL_KHR_gl_texture_cubemap_image EGL_KHR_gl_renderbuffer_image EGL_KHR_get_all_proc_addresses EGL_KHR_stream EGL_KHR_stream_consumer_gltexture EGL_NV_stream_consumer_gltexture_yuv EGL_ANGLE_flexible_surface_compatibility EGL_ANGLE_stream_producer_d3d_texture EGL_ANGLE_create_context_webgl_compatibility EGL_CHROMIUM_create_context_bind_generates_resource EGL_CHROMIUM_sync_control EGL_EXT_pixel_format_float EGL_KHR_surfaceless_context EGL_ANGLE_display_texture_share_group EGL_ANGLE_create_context_client_arrays EGL_ANGLE_program_cache_control EGL_ANGLE_robust_resource_initialization EGL_ANGLE_create_context_extensions_enabled EGL_MOZ_create_context_provoking_vertex_dont_care EGL_EXTENSIONS(nullptr): EGL_EXT_client_extensions EGL_EXT_platform_base EGL_EXT_platform_device EGL_ANGLE_platform_angle EGL_ANGLE_platform_angle_d3d EGL_ANGLE_device_creation EGL_ANGLE_device_creation_d3d11 EGL_ANGLE_experimental_present_path EGL_KHR_client_get_all_proc_addresses EGL_KHR_debug EGL_ANGLE_explicit_context
WebGL 2 Driver Renderer: Google Inc. -- ANGLE (Intel(R) UHD Graphics 630 Direct3D11 vs_5_0 ps_5_0)
WebGL 2 Driver Version: OpenGL ES 3.0 (ANGLE 2.1.0.eff6bfdb1db9)
WebGL 2 Driver Extensions: GL_ANGLE_client_arrays GL_ANGLE_depth_texture GL_ANGLE_explicit_context GL_ANGLE_explicit_context_gles1 GL_ANGLE_framebuffer_blit GL_ANGLE_framebuffer_multisample GL_ANGLE_instanced_arrays GL_ANGLE_lossy_etc_decode GL_ANGLE_multiview GL_ANGLE_pack_reverse_row_order GL_ANGLE_program_cache_control GL_ANGLE_request_extension GL_ANGLE_robust_client_memory GL_ANGLE_texture_compression_dxt3 GL_ANGLE_texture_compression_dxt5 GL_ANGLE_texture_usage GL_ANGLE_translated_shader_source GL_CHROMIUM_bind_generates_resource GL_CHROMIUM_bind_uniform_location GL_CHROMIUM_color_buffer_float_rgb GL_CHROMIUM_color_buffer_float_rgba GL_CHROMIUM_copy_compressed_texture GL_CHROMIUM_copy_texture GL_CHROMIUM_sync_query GL_EXT_blend_minmax GL_EXT_color_buffer_float GL_EXT_color_buffer_half_float GL_EXT_debug_marker GL_EXT_discard_framebuffer GL_EXT_disjoint_timer_query GL_EXT_draw_buffers GL_EXT_frag_depth GL_EXT_map_buffer_range GL_EXT_occlusion_query_boolean GL_EXT_read_format_bgra GL_EXT_robustness GL_EXT_sRGB GL_EXT_shader_texture_lod GL_EXT_texture_compression_dxt1 GL_EXT_texture_compression_s3tc_srgb GL_EXT_texture_filter_anisotropic GL_EXT_texture_format_BGRA8888 GL_EXT_texture_norm16 GL_EXT_texture_rg GL_EXT_texture_storage GL_EXT_unpack_subimage GL_KHR_debug GL_KHR_parallel_shader_compile GL_KHR_robust_buffer_access_behavior GL_NV_EGL_stream_consumer_external GL_NV_fence GL_NV_pack_subimage GL_NV_pixel_buffer_object GL_OES_EGL_image GL_OES_EGL_image_external GL_OES_EGL_image_external_essl3 GL_OES_compressed_ETC1_RGB8_texture GL_OES_depth32 GL_OES_element_index_uint GL_OES_get_program_binary GL_OES_mapbuffer GL_OES_packed_depth_stencil GL_OES_rgb8_rgba8 GL_OES_standard_derivatives GL_OES_surfaceless_context GL_OES_texture_float GL_OES_texture_float_linear GL_OES_texture_half_float GL_OES_texture_half_float_linear GL_OES_texture_npot GL_OES_vertex_array_object OES_compressed_EAC_R11_signed_texture OES_compressed_EAC_R11_unsigned_texture OES_compressed_EAC_RG11_signed_texture OES_compressed_EAC_RG11_unsigned_texture OES_compressed_ETC2_RGB8_texture OES_compressed_ETC2_RGBA8_texture OES_compressed_ETC2_punchthroughA_RGBA8_texture OES_compressed_ETC2_punchthroughA_sRGB8_alpha_texture OES_compressed_ETC2_sRGB8_alpha8_texture OES_compressed_ETC2_sRGB8_texture
WebGL 2 Extensions: EXT_color_buffer_float EXT_disjoint_timer_query EXT_texture_filter_anisotropic OES_texture_float_linear WEBGL_compressed_texture_s3tc WEBGL_compressed_texture_s3tc_srgb WEBGL_debug_renderer_info WEBGL_debug_shaders WEBGL_lose_context
Direct2D: true
Uses Tiling (Content): true
Off Main Thread Painting Enabled: true
Off Main Thread Painting Worker Count: 4
Target Frame Rate: 60
DirectWrite: true (10.0.18342.1)
GPU #1
Active: Yes
Description: Intel(R) UHD Graphics 630
Vendor ID: 0x8086
Device ID: 0x3e9b
Driver Version: 25.20.100.6471
Driver Date: 12-10-2018
Drivers: igdumdim64 igd10iumd64 igd10iumd64 igd12umd64 igdumdim32 igd10iumd32 igd10iumd32 igd12umd32
Subsys ID: 087c1028
RAM: Unknown
GPU #2
Active: No
Description: NVIDIA GeForce GTX 1050 Ti with Max-Q Design
Vendor ID: 0x10de
Device ID: 0x1c8c
Driver Version: 24.21.13.9793
Driver Date: 5-22-2018
Drivers: C:\WINDOWS\System32\DriverStore\FileRepository\nvdm.inf_amd64_786f30519164c09a\nvldumdx.dll,C:\WINDOWS\System32\DriverStore\FileRepository\nvdm.inf_amd64_786f30519164c09a\nvldumdx.dll,C:\WINDOWS\System32\DriverStore\FileRepository\nvdm.inf_amd64_786f30519164c09a\nvldumdx.dll,C:\WINDOWS\System32\DriverStore\FileRepository\nvdm.inf_amd64_786f30519164c09a\nvldumdx.dll C:\WINDOWS\System32\DriverStore\FileRepository\nvdm.inf_amd64_786f30519164c09a\nvldumd.dll,C:\WINDOWS\System32\DriverStore\FileRepository\nvdm.inf_amd64_786f30519164c09a\nvldumd.dll,C:\WINDOWS\System32\DriverStore\FileRepository\nvdm.inf_amd64_786f30519164c09a\nvldumd.dll,C:\WINDOWS\System32\DriverStore\FileRepository\nvdm.inf_amd64_786f30519164c09a\nvldumd.dll
Subsys ID: 087c1028
RAM: 4096
Diagnostics
ClearType Parameters: Gamma: 1.8 Pixel Structure: RGB ClearType Level: 100 Enhanced Contrast: 50
AzureCanvasBackend: direct2d 1.1
AzureCanvasBackend (UI Process): skia
AzureContentBackend: skia
AzureContentBackend (UI Process): skia
AzureFallbackCanvasBackend (UI Process): cairo
Slow Frame #01: Frame 426(https://hg.mozilla.org/mozilla-central/pushloghtml?changeset=42f9208ed5f3f4c98374661d05c5c74b8df4ff70) CONTENT_FRAME_TIME 596008 - Transaction start 0.000000, main-thread time 9.737700, full paint time 15.279300, Skipped composites 0, Composite start 19.831500, Resource upload time 0.000700, GPU cache upload time 0.262900, Render time 6.024300, Composite time 14.020700
Slow Frame #02: Frame 97(https://hg.mozilla.org/mozilla-central/rev/f900bfeeb59c) CONTENT_FRAME_TIME 587088 - Transaction start 0.000000, main-thread time 23.320900, full paint time 29.472500, Skipped composites 0, Composite start 42.093700, Resource upload time 0.000700, GPU cache upload time 0.357300, Render time 13.853800, Composite time 28.114300
Slow Frame #03: Frame 52(https://hg.mozilla.org/mozilla-central/rev/fe805cb52ee2) CONTENT_FRAME_TIME 468391 - Transaction start 0.000000, main-thread time 15.906800, full paint time 24.732800, Skipped composites 0, Composite start 31.385000, Resource upload time 0.701300, GPU cache upload time 0.302600, Render time 6.796800, Composite time 12.261300
Slow Frame #04: Frame 306(https://hg.mozilla.org/mozilla-central/pushloghtml?changeset=42f9208ed5f3f4c98374661d05c5c74b8df4ff70) CONTENT_FRAME_TIME 466602 - Transaction start 0.000000, main-thread time 5.603700, full paint time 7.587500, Skipped composites 0, Composite start 15.455500, Resource upload time 0.000700, GPU cache upload time 0.191600, Render time 11.455500, Composite time 16.106100
Slow Frame #05: Frame 81(https://hg.mozilla.org/mozilla-central/rev/f900bfeeb59c) CONTENT_FRAME_TIME 406408 - Transaction start 0.000000, main-thread time 23.066300, full paint time 28.897400, Skipped composites 0, Composite start 37.370900, Resource upload time 0.000700, GPU cache upload time 0.262900, Render time 6.024300, Composite time 14.020700
Slow Frame #06: Frame 179(https://hg.mozilla.org/mozilla-central/pushloghtml?changeset=42f9208ed5f3f4c98374661d05c5c74b8df4ff70) CONTENT_FRAME_TIME 337384 - Transaction start 0.000000, main-thread time 6.465100, full paint time 9.588400, Skipped composites 0, Composite start 10.120700, Resource upload time 0.000900, GPU cache upload time 0.378700, Render time 4.845100, Composite time 12.304500
Slow Frame #07: Frame 147(https://hg.mozilla.org/mozilla-central/pushloghtml?changeset=42f9208ed5f3f4c98374661d05c5c74b8df4ff70) CONTENT_FRAME_TIME 317693 - Transaction start 0.000000, main-thread time 7.789800, full paint time 14.371500, Skipped composites 0, Composite start 28.891300, Resource upload time 0.574200, GPU cache upload time 0.469800, Render time 5.629800, Composite time 10.062500
Slow Frame #08: Frame 36(https://github.com/mozilla-mobile/android-components/issues/1346) CONTENT_FRAME_TIME 265519 - Transaction start 0.000000, main-thread time 14.253000, full paint time 21.597200, Skipped composites 0, Composite start 29.109400, Resource upload time 0.001000, GPU cache upload time 0.380300, Render time 12.024100, Composite time 17.726600
Slow Frame #09: Frame 45(https://github.com/mozilla-mobile/android-components/issues/1385) CONTENT_FRAME_TIME 234292 - Transaction start 0.000000, main-thread time 20.618700, full paint time 29.055600, Skipped composites 0, Composite start 30.541100, Resource upload time 14.104700, GPU cache upload time 0.487400, Render time 26.476800, Composite time 46.205400
Slow Frame #10: Frame 54(https://hg.mozilla.org/mozilla-central/rev/fe805cb52ee2) CONTENT_FRAME_TIME 158577 - Transaction start 0.000000, main-thread time 9.942100, full paint time 12.868800, Skipped composites 0, Composite start 19.487600, Resource upload time 0.000700, GPU cache upload time 0.318500, Render time 5.092100, Composite time 9.058400
GPUProcessPid: 15456
GPUProcess: Terminate GPU Process
Device Reset: Trigger Device Reset
ClearType Parameters: Gamma: 1.8 Pixel Structure: RGB ClearType Level: 100 Enhanced Contrast: 50
Decision Log
WEBRENDER:
opt-in by default: WebRender is an opt-in feature
available by user: Force enabled by pref
WEBRENDER_QUALIFIED:
blocked by env: Has battery

Hi Chris, I have tried to reproduce the bug described in comment 0 with Nightly 67.0a1 (2019-03-04) on the latest Insider Preview build 18343.1.19h1_release.190219-1422. It seems that the carets are not jumping back on my end after typing some random characters (~25) in a textarea; tried so far on slack, bugzilla and a textarea testcase, having the gfx.webrender.all enabled.

Maybe, it's an issue indeed with the Windows 10 Insider Preview as you already said, in that case could you please re-check the steps after updating your build to the latest previews available. Thank you!

My Windows laptop was just updated from Windows 10 Insider Preview build 18342.19h1_release.190215-1528 to 18351.19h1_release.190301-1611. I can still reproduce this flashing text issue.

I have also attempted to reproduce your issue with no luck.
I need to ask you about any details that might influence the reproduction:

1. Which version of Windows 10 do you have? (Settings/System/About) Is it OS build? Version?
2. Please see it this reproduces in a newly created profile if your reproduction is on a used/old profile.
3. Are there any other details that you might have missed that would be important to the reproduction?
4. Did you only test it in Nightly 67? Can you also test Nightly 68 and Release 66?

Thank you!

(In reply to Bodea Daniel [:danibodea] from comment #3)

1. Which version of Windows 10 do you have? (Settings/System/About) Is it OS build? Version?

I'm currently using Windows 10 Insider Preview 10.0.18362.30 (19h1_release) from 2019-04-05.

2. Please see it this reproduces in a newly created profile if your reproduction is on a used/old profile.
3. Are there any other details that you might have missed that would be important to the reproduction?
4. Did you only test it in Nightly 67? Can you also test Nightly 68 and Release 66?

Yes. I can reproduce in Nightly 68 and Release 66 with WebRender enabled with a new profile. However, the caret jumping problem is much, much better. It's not nearly noticeable as it used to be, especially with a new profile.

I'll close this bug as WORKSFORME for now. I don't think it's worth your time to debug the very minor problem I currently see.