Created attachment 164704 [details] images containing the issue. SUMMARY When using the my tablet (samsung galaxy tab s8 ultra) to draw, on the left side of the screen there seems to be a bug where on certain spots it gives uneven pressure, I have tested on two different tablets, S8 ultra, and S9 ultra, both exhibit the same issue with the default pressure curve of the tools that have anything else than a linear curve, see attached photos. Troubleshooting includes: 1. tested different tablet with same version of krita, -> same issue 2. tested with a different S-pen on both of those tablets -> same issue 3. uninstalled krita, removing all data associated with it, and reinstalled it -> same issue 4. tested different brushes and tools in krita, brushes with non-linear curves exhibits the problems. 5. made brushes have a linear curve from 0 - 100, with just 2 points -> issue resolved as a bypass STEPS TO REPRODUCE 1. Have a tablet with wacom support on android 13.x (I believe any android tablet with wacom style pens work) 2. set brush pixel size to be 50 or more so problem can be visible 3. use any pen that has a different curve for their size than linear, for example the fountain pen. 4. draw lines going down from the top, with an even pressure and observe the pressure changing by itself. OBSERVED RESULT see images attached EXPECTED RESULT expected result is to have the pen pressure in that region not change as you move over a specific part with even pressure, see images for explanation. SOFTWARE/OS VERSIONS Android 13 Qt Version: 5.15.7 ADDITIONAL INFORMATION Krita Version: 5.2.2 Hidpi: true Qt Version (compiled): 5.15.7 Version (loaded): 5.15.7 OS Information Build ABI: arm64-little_endian-lp64 Build CPU: arm64 CPU: arm64 Kernel Type: linux Kernel Version: 5.10.136-android12-9-27102101-abX906BXXS5BWI1 Pretty Productname: Android (13.0) Product Type: android Product Version: 13.0 Product Model: Samsung SM-X906B Locale Languages: en_GB, en_Latn_GB C locale: C.UTF-8 QLocale current: en QLocale system: en QTextCodec for locale: UTF-8 OpenGL Info Vendor: "Qualcomm" Renderer: "Adreno (TM) 730" Driver version: "OpenGL ES 3.2 V@0615.0 (GIT@5a00bbd4b7, I0f5aa60515, 1673930385) (Date:01/16/23)" Shading language: "OpenGL ES GLSL ES 3.20" Requested format: QSurfaceFormat(version 3.0, options QFlags<QSurfaceFormat::FormatOption>(), depthBufferSize 24, redBufferSize 8, greenBufferSize 8, blueBufferSize 8, alphaBufferSize 8, stencilBufferSize 8, samples -1, swapBehavior QSurfaceFormat::DoubleBuffer, swapInterval 0, colorSpace QSurfaceFormat::DefaultColorSpace, profile QSurfaceFormat::NoProfile) Current format: QSurfaceFormat(version 3.2, options QFlags<QSurfaceFormat::FormatOption>(), depthBufferSize 24, redBufferSize 8, greenBufferSize 8, blueBufferSize 8, alphaBufferSize 8, stencilBufferSize 8, samples 0, swapBehavior QSurfaceFormat::DefaultSwapBehavior, swapInterval 0, colorSpace QSurfaceFormat::DefaultColorSpace, profile QSurfaceFormat::NoProfile) GL version: 3.2 Supports deprecated functions false Is OpenGL ES: true supportsBufferMapping: true supportsBufferInvalidation: false forceDisableTextureBuffers: false Extensions: GL_EXT_clip_control GL_KHR_texture_compression_astc_hdr GL_OES_texture_compression_astc GL_EXT_primitive_bounding_box GL_EXT_protected_textures GL_EXT_texture_sRGB_decode GL_OES_shader_multisample_interpolation GL_KHR_robust_buffer_access_behavior GL_QCOM_validate_shader_binary GL_OES_framebuffer_object GL_EXT_color_buffer_float GL_OES_depth24 GL_EXT_discard_framebuffer GL_QCOM_texture_foveated2 GL_EXT_draw_buffers_indexed GL_OES_texture_float GL_ARM_shader_framebuffer_fetch_depth_stencil GL_OES_texture_npot GL_EXT_read_format_bgra GL_OES_texture_half_float_linear GL_QCOM_tiled_rendering GL_EXT_memory_object_fd GL_OES_sample_shading GL_OES_EGL_image GL_EXT_texture_buffer GL_EXT_fragment_invocation_density GL_EXT_external_buffer GL_EXT_texture_type_2_10_10_10_REV GL_OES_vertex_array_object GL_ANDROID_extension_pack_es31a GL_EXT_sRGB GL_EXT_texture_cube_map_array GL_KHR_texture_compression_astc_ldr GL_EXT_debug_label GL_OES_texture_3D GL_OES_standard_derivatives GL_OES_rgb8_rgba8 GL_EXT_disjoint_timer_query GL_OES_texture_half_float GL_EXT_blit_framebuffer_params GL_EXT_EGL_image_storage GL_EXT_gpu_shader5 GL_EXT_buffer_storage GL_QCOM_shader_framebuffer_fetch_noncoherent GL_OES_vertex_half_float GL_EXT_shader_non_constant_global_initializers GL_OES_shader_image_atomic GL_EXT_shader_io_blocks GL_OES_EGL_image_external_essl3 GL_QCOM_shader_framebuffer_fetch_rate GL_QCOM_render_shared_exponent GL_QCOM_texture_foveated GL_OES_EGL_image_external GL_AMD_compressed_ATC_texture GL_OES_texture_storage_multisample_2d_array GL_EXT_sRGB_write_control GL_QCOM_shading_rate GL_EXT_EGL_image_array GL_EXT_copy_image GL_KHR_blend_equation_advanced_coherent GL_OES_texture_float_linear GL_OES_depth_texture_cube_map GL_QCOM_motion_estimation GL_QCOM_YUV_texture_gather GL_EXT_tessellation_shader GL_KHR_blend_equation_advanced GL_EXT_texture_sRGB_R8 GL_EXT_texture_format_sRGB_override GL_EXT_EGL_image_external_wrap_modes GL_EXT_clip_cull_distance GL_EXT_texture_format_BGRA8888 GL_EXT_texture_norm16 GL_OES_surfaceless_context GL_OES_element_index_uint GL_QCOM_frame_extrapolation GL_KHR_debug GL_OES_EGL_sync GL_OES_compressed_ETC1_RGB8_texture GL_OES_texture_view GL_OES_texture_stencil8 GL_EXT_memory_object GL_EXT_robustness GL_OVR_multiview2 GL_OVR_multiview_multisampled_render_to_texture GL_EXT_shader_framebuffer_fetch GL_EXT_blend_func_extended GL_EXT_texture_filter_anisotropic GL_OES_packed_depth_stencil GL_OES_get_program_binary GL_EXT_YUV_target GL_IMG_texture_filter_cubic GL_OES_sample_variables GL_EXT_multisampled_render_to_texture2 GL_EXT_texture_border_clamp GL_NV_shader_noperspective_interpolation GL_KHR_no_error GL_QCOM_alpha_test GL_EXT_geometry_shader GL_EXT_multisampled_render_to_texture GL_EXT_debug_marker GL_EXT_color_buffer_half_float GL_OES_depth_texture GL_OVR_multiview GL_QCOM_texture_foveated_subsampled_layout QPA OpenGL Detection Info supportsDesktopGL: false supportsOpenGLES: true isQtPreferOpenGLES: true Detected renderers: (Supported) Adreno (TM) 730 (OpenGL ES 3.2 V@0615.0 (GIT@5a00bbd4b7, I0f5aa60515, 1673930385) (Date:01/16/23)) useBufferInvalidation (config option): false Hardware Information GPU Acceleration: auto Memory: 7300 Mb Number of Cores: 8 Swap Location: /data/data/org.krita/cache Built for: arm64+neon Base instruction set: arm64+neon Supported instruction sets: arm64+neon arm32+neon avx512bw avx512dq avx512cd avx512f fma3+avx2 avx2 fma3+avx avx fma4 fma3+sse4.2 sse4.2 sse4.1 ssse3 sse3 sse2 Current Settings Current Swap Location: /data/data/org.krita/cache Current Swap Location writable: true Undo Enabled: true Undo Stack Limit: 200 Use OpenGL: true Use OpenGL Texture Buffer: true Disable Vector Optimizations: false Disable AVX Optimizations: false Canvas State: OPENGL_NOT_TRIED Autosave Interval: 420 Use Backup Files: true Number of Backups Kept: 1 Backup File Suffix: ~ Backup Location: Same Folder as the File Backup Location writable: false Resource Location: Use Win8 Pointer Input: false Use RightMiddleTabletButton Workaround: false Levels of Detail Enabled: false Use Zip64: false Display Information Number of screens: 1 Screen: 0 Name: Depth: 32 Scale: 2 Physical DPI120.01 Logical DPI72 Physical Size: 314, 182 Position: 0, 0 Resolution in pixels: 1480x862 Manufacturer: Model: Refresh Rate: 60 Serial Number: Current Settings Current Swap Location: /data/data/org.krita/cache Current Swap Location writable: true Undo Enabled: true Undo Stack Limit: 200 Use OpenGL: true Use OpenGL Texture Buffer: true Disable Vector Optimizations: false Disable AVX Optimizations: false Canvas State: TRY_OPENGL Autosave Interval: 420 Use Backup Files: true Number of Backups Kept: 1 Backup File Suffix: ~ Backup Location: Same Folder as the File Backup Location writable: false Resource Location: /storage/emulated/0/Android/data/org.krita/files Use Win8 Pointer Input: false Use RightMiddleTabletButton Workaround: false Levels of Detail Enabled: false Use Zip64: false --------------------- ================================================================================ SESSION: 06 Jan 2024 12:05:30 +0100. Executing /data/app/~~jWEmgSF6Nf7iAVWLDgwRIQ==/org.krita-zvB7PZ1VIDojuZ829RZzQA==/lib/arm64/libkrita_arm64-v8a.so Krita Version: 5.2.2, Qt version compiled: 5.15.7, loaded: 5.15.7. Process ID: 8957 -- -- -- -- -- -- -- -- 06 Jan 2024 12:05:30 +0100: Style: fusion. Available styles: android, Windows, Fusion 06 Jan 2024 12:05:31 +0100: Creating database from scratch (database didn't exist, new schema version: 0.0.17). 06 Jan 2024 12:05:44 +0100: Created image "Unnamed", 2480 * 3508 pixels, 300 dpi. Color model: 8-bit integer/channel RGB/Alpha (sRGB-elle-V2-srgbtrc.icc). Layers: 2 06 Jan 2024 12:07:56 +0100: Converting from application/x-krita to application/x-krita. Location: /storage/emulated/0/Android/data/org.krita/files/Documents/krita-backup/.krita-8957-document_0-autosave.kra. Real location: /storage/emulated/0/Android/data/org.krita/files/Documents/krita-backup/.krita-8957-document_0-autosave.kra. Batchmode: 0. Configuration: none 06 Jan 2024 12:12:35 +0100: Removing autosave file: /storage/emulated/0/Android/data/org.krita/files/Documents/krita-backup/.krita-8957-document_0-autosave.kra 06 Jan 2024 12:13:11 +0100: Created image "Unnamed", 2480 * 3508 pixels, 300 dpi. Color model: 8-bit integer/channel RGB/Alpha (sRGB-elle-V2-srgbtrc.icc). Layers: 2 ---------------------
As far as I know, Krita manages the tablet equally across the canvas. So if you experience a bug that affects only a part or specific spot of the canvas, e.g. a pressure change that affects only a region as you describe, it's most likely caused by bad engineering at the hardware level. I'm sorry. It could be bad electromagnetic shielding of the display, or a connector in that area that is leaking and affecting the pressure sensitivity, I have never seen this happen specifically to "pressure only" with Wacom's EMR (electromagnetic resonance) based device. (I'm assuming here that the Samsung Android tablets use EMR technology for their pen). The classic problem I see when bad shielding is done at the engineering of the tablet is mostly line shaking, and a line jittering with the noise. So, I'm not sure what is exactly happening in your case. Can you reproduce the issue with another painting software using pressure sensitivity? That would at least confirm it is a bug hardware specific.
(In reply to David REVOY from comment #1) > As far as I know, Krita manages the tablet equally across the canvas. So if > you experience a bug that affects only a part or specific spot of the > canvas, e.g. a pressure change that affects only a region as you describe, > it's most likely caused by bad engineering at the hardware level. > I'm sorry. > It could be bad electromagnetic shielding of the display, or a connector in > that area that is leaking and affecting the pressure sensitivity, > I have never seen this happen specifically to "pressure only" with Wacom's > EMR (electromagnetic resonance) based device. (I'm assuming here that the > Samsung Android tablets use EMR technology for their pen). The classic > problem I see when bad shielding is done at the engineering of the tablet is > mostly line shaking, and a line jittering with the noise. So, I'm not sure > what is exactly happening in your case. > > Can you reproduce the issue with another painting software using pressure > sensitivity? > That would at least confirm it is a bug hardware specific. I have tried a few different ones, namely hipaint, Medibang, sketchbook (from Autodesk I think) I have not experienced any problems in those applications. I also have a video of the issue, to show own it appears.
Actually please disregard this report, I've done more testing, and it turns out there is a magnetic force in the tablet around that area and I tested with some more drawing software, it seems it is present on those too, albeit less noticeable, I am sorry for making a report on something that seems to be with the tablet.
Thanks for your comment! Automatically switching the status of this bug to REPORTED so that the KDE team knows that the bug is ready to get confirmed. In the future you may also do this yourself when providing needed information.